Questions and Answers about COVID-19 Vaccines

On this page, you will find answers to some of the most common questions people are asking about COVID-19 disease and vaccines. Just click on the question of interest and the answer will appear below it. 

Can't find what you're looking for?

  1. Check the “Archived COVID-19 Questions” page.
  2. Ask your COVID-19 vaccine questions here.

You can also find information related to COVID-19 on our printable Q&A, "COVID-19 mRNA vaccines: What you should know" (also available in Spanish and Japanese) and our “Look at Each Vaccine: COVID-19 Vaccine” webpage.

July 29, 2021:
Wondering how the mRNA vaccines are processed? Check out our newly released animation,
“How mRNA Vaccines Work.”

Do I need a third dose of the COVID-19 vaccine?

While most people do not currently need an additional dose of the COVID-19 vaccine, the Centers for Disease Control and Prevention (CDC) recently indicated a third dose for a small group of people. This decision was based on findings that the immune response following receipt of two doses of mRNA vaccine in some people whose immune systems are compromised is not as robust as the responses found in similar people whose immune systems are not compromised. While this additional dose has been portrayed as a “booster dose,” it is, in fact, meant to be an additional primary dose for these individuals. While the end result is likely the same – a higher level of immunity – the difference between a booster and an additional primary dose is an important distinction for the great majority of us. Specifically:

  • Booster - A booster would be indicated for waning immunity or changes to the virus that make existing immunity less capable of preventing severe disease and death.
  • Additional primary dose - An additional primary dose is indicated if the immune response never reaches sufficient levels of protection. Said another way, some groups of people have received the two doses of mRNA vaccine and because their immune system is compromised, they never developed the same level of immunity that most of us did. It is for this reason that the additional dose is being recommended, but only for certain people.

People who should get an additional dose of COVID-19 vaccine:

  • People currently being treated for cancers of the blood or organs (so-called “solid tumor” cancers)
  • People who received an organ transplant and take immunosuppressive medications to prevent rejection of the organ
  • People who had a stem cell transplant or received CAR-T-cell therapy less than 2 years ago or who are taking immunosuppressive medications
  • People with conditions that are considered to cause permanent immune deficiency because the condition affects cells of their immune system, such as DiGeorge syndrome or Wiskott-Aldrich syndrome
  • People infected with HIV whose infection is untreated or considered to be at an advanced stage
  • People currently being treated with one of the following types of medications:
    • High-dose corticosteroids (more than 20 mg prednisone or similar medications per day)
    • Alkylating agents
    • Antimetabolites
    • Transplant-related immunosuppressive medications
    • Cancer chemotherapeutic medications that are considered severely immunosuppressive (e.g., tumor-necrosis, or TNF, blockers)
    • Biologic agents that suppress or modulate the immune response

People who should speak to their healthcare provider to decide together if they need an additional dose of COVID-19 vaccine:

Because immune-compromising conditions are variable in the extent to which the immune system is compromised, many people who might be considered to have some level of immune compromise would not fall into the categories listed above. As such, if you have questions, it is recommended that you contact your treating healthcare provider for help sorting out whether you would be included in the group recommended to get an additional dose of COVID-19 mRNA vaccine. Such people might include:

  • People taking medications that make them uncertain whether they would be included in the list of individuals mentioned above
  • People with immune-system-related conditions not specifically mentioned above
  • People preparing to start one of the above-mentioned medications

People who should NOT get an additional dose of COVID-19 vaccine at this time:

  • Immune-compromised people who received the J&J/Janssen vaccine – Data are still being accumulated and this recommendation will change if findings are similar to those with the mRNA vaccines.
  • People who do not have compromised immunity.
  • People without a spleen.
  • People who had cancer but are no longer being treated.
  • People with chronic conditions that do not involve the immune system or require treatment with high doses of corticosteroids, such as diabetes, asthma, COPD, kidney disease, heart conditions, sickle cell disease, among others. If you are not sure, check with your healthcare provider.

For those indicated to get the additional dose of COVID-19 vaccine, the additional dose should be administered at least 28 days after the second dose and should be of the same type of mRNA vaccine given previously, if possible.

Finally, people with compromised immunity, and their close contacts, are recommended to continue layering protection by masking, staying 6 feet apart from others, and avoiding crowds or poorly ventilated indoor spaces, particularly in areas where the virus is widespread. Data will be collected to determine whether the third dose generates levels of immunity that are protective, but in the meantime, extra caution is still advised.

Watch this short video in which Dr. Offit explains why a third dose of COVID-19 vaccine is being considered and what to expect.

Last updated: 8/16/21

When will COVID-19 vaccines be available for children younger than 12 years of age?

COVID-19 vaccine trials are in progress for children but have not yet been completed. The anticipated timeline would be that by fall some of the first data will be available for review (probably for 6- to 12-year-olds). If approved for use (licensed or authorized), it is possible that vaccinations could begin by late fall, but this will depend on a number of things, such as when the data are submitted for review and how long it takes for the review process to be completed.

Find out more about COVID-19 clinical trials in children in this recent Parents PACK article, including how the trials are being done, what will be learned and more.

Last updated: 8/10/2021

What is the difference between emergency use authorization and the normal process of vaccine approval?

The main difference between emergency use authorization, or EUA, and the normal process, which is via a biologic licensure application, or BLA, is how long data were collected prior to the vaccines being reviewed for use. So, when considered quite literally, the vaccines being used today (under EUA) will be no different than those that are being used the day after the vaccines get full approval (BLA). The reason for the shortened timeline was, of course, because of the pandemic. But, at this point, the vaccines have been given safely to millions of people and the companies have been monitoring vaccine recipients for months. As such, at this point, delaying vaccination until the vaccines get “full approval” is taking an unnecessary risk.

Last updated: 8/10/21

Were the COVID-19 vaccines approved by the FDA?

Even though the COVID-19 vaccines were released under Emergency Use Authorization (EUA), they were still approved by the Food and Drug Administration (FDA). The review process was the same, but because of the pandemic, the data could be submitted after a shorter period of participant follow-up than usual. However, even after submitting data (and getting an EUA), those studies continued and at some point, the companies will submit the additional follow-up data to request licensure under Biologics Licensure Application (BLA).

Last updated: 8/10/21

Is it safe for my teen to get the COVID-19 vaccine given the stories about myocarditis?

Cases of myocarditis, or inflammation of the heart, have been reported in teens after receipt of the COVID-19 mRNA vaccine. The condition is continuing to be investigated. Here is what we know to date:

  • Emerging data from the Vaccine Safety DataLink (VSD) suggest that the rates are higher than have been found in a non-vaccinated population.
  • The cases of myocarditis that have occurred so far were more often in boys and young men and more often after the second dose. Symptoms occurred within 4 days after receipt of the dose. Recently immunized teens and young adults who experience chest pain or shortness of breath should be seen by a healthcare provider and report recent their vaccination.
  • Myocarditis is somewhat common, particularly as a result of viral infections. In fact, cases tend to occur more often in the spring due to viruses that circulate at this time of year (specifically, coxsackie B viruses). Typically, about 100-200 cases occur per million people per year.
  • To date, about 306 million doses of the COVID-19 vaccines have been given, and about 7.2 million of these have been in teens (12-18 years old).
  • Available data suggest that the incidence of myocarditis following mRNA vaccines is about 1 per 50,000 vaccine recipients. Of interest, myocarditis also occurs more commonly after either acute COVID-19 or as part of the multisystem inflammatory syndrome of children (MIS-C).
  • Parents and teens should watch for symptoms that may include chest pain, pressure, heart palpitations, difficulty breathing after exercise or lying down, or excessive sweating. One or more of these symptoms may also be accompanied by tiredness, stomach pain, dizziness, fainting, unexplained swelling, or coughing. If a recently vaccinated teen develops these symptoms or you are unsure, contact the child’s doctor or seek more immediate medical assistance if needed.

The CDC will continue to monitor the situation related to myocarditis, but for now, there is not a reason to stop vaccinating kids. The American Heart Association has also released a statement encouraging continued vaccination.

In this short video, Dr. Paul Offit discusses myocarditis related to receipt of the COVID-19 vaccine.

Last updated: June 14, 2021

Can I get the COVID-19 vaccine if I have COVID-19?

In the U.S., the CDC recommends waiting until COVID-19 symptoms go away and the individual is done isolating. However, they indicate that it is okay to get the COVID-19 vaccine shortly after recovering from the disease as long as the patient was not treated with antibody-based treatments (convalescent plasma or monoclonal antibodies).

Due to limited supplies of vaccine in some countries and the experience that people who recently had COVID-19 rarely get re-infected in the months immediately after recovery, some areas may be delaying vaccination of recently recovered individuals. As such, we recommend talking with your healthcare provider or health officials to see what the recommendations are in your area.

Last updated 8/10/21

Is it safe for my adolescent or teen to get the COVID-19 vaccine?

The Pfizer COVID-19 mRNA vaccine is approved for those 12 years of age and older. Other COVID-19 vaccines are still being tested in those younger than 18 years of age.
When the Pfizer vaccine was tested in 12- to 18-year-olds, it was found to be safe:

  • Those 16- to 18-years old were included in the trials presented to the FDA in December 2020. Since then, more than 2 million teens had received one dose of the vaccine, and more than 1 million had received both doses by May 12, 2021 – the date that the vaccine was approved for 12- to 15-year-olds.
  • The clinical trial in 12- to 15-year-olds evaluated about 1,100 children who received the vaccine and compared them with about the same number who got placebo (a salt solution) as well as almost 2,000 16- to 25-year-olds who were vaccinated and about the same number in an age-matched placebo group. No vaccinated individuals got infected with COVID-19 or experienced severe side effects, like anaphylactic allergic reaction. A small number experienced swelling under the arm on the side in which the vaccine was administered. Called lymphadenopathy, this can also occur in adults who get the mRNA vaccines. This side effect occurred 2-10 days after vaccination and typically lasted up to 10 days.  Trial participants will continue to be followed for up to two years.
  • As increasing numbers of teens have been vaccinated, a few cases of myocarditis have been identified. It appears that the rates are greater than would be expected, so additional efforts are being made to identify this condition following receipt of the mRNA vaccine. Recently vaccinated young adults should report chest pain or shortness of breath following receipt of the COVID-19 vaccine, so that they can receive appropriate care and cases are accurately reflected to determine if this is caused by receipt of the vaccine. Find out more in this video.

For general information about what teens can expect when they go for their COVID-19 vaccine, check out the Vaccine Makers Project (VMP) article. The VMP is the VEC’s classroom program. 

Last updated: June 14, 2021

What side effects will my child experience from the COVID-19 vaccine?

Side effects in children 12 to 15 years of age were similar to what has been found in other age groups, including pain at the injection site, fatigue, headache, fever, chills, muscle pain, or joint pain. Likewise, other than injection site pain, side effects were more common after the second dose compared with the first dose. Most side effects were mild or moderate.

No one in the study experienced an allergic reaction following vaccination, but this age group is not less likely to experience such a reaction; therefore, teenagers should remain at the site where the vaccine was given for 15 or 30 minutes based on their risk and history with severe allergic reactions using the same guidance offered for adults. (See “If a person has allergic reactions to a food or medication can they get the vaccine?” for more details.)

Recently, a small number of cases of myocarditis, or heart inflammation, have been identified in teens and young adults, particularly in the 4 days after receipt of the second dose of the vaccine. Chest pain, shortness of breath, or related symptoms should be reported to a healthcare provider, so that teens can be appropriately diagnosed and treated. Find out more in this video.

Find additional information:

Last updated: June 14, 2021

If a person has allergic reactions to a food or medication, can they get the vaccine?

People with severe allergies to a COVID-19 vaccine ingredient (see list here) or a previous dose of COVID-19 vaccine should not get that type of COVID-19 vaccine (mRNA or adenovirus-based). They may be able to get the alternative type after consultation with an allergist or immunologist. Individuals with a known allergy to polysorbate should not get the COVID-19 vaccine made by Johnson & Johnson/Janssen.

People with immediate allergic reactions to an injectable medication can most often get the COVID-19 vaccine; however, they should remain at the site where they were vaccinated for 30 minutes of observation, instead of the 15 minutes that the general public is recommended to wait. Anyone with this type of allergy who has questions or concerns should discuss the situation with their healthcare provider to assess the potential risks and benefits of receiving the COVID-19 vaccine. 

People who have had an anaphylactic reaction to anything else (medications, foods, bees, etc.) are allowed to get the COVID-19 vaccine, but should remain at the site where the injection was given for 30 minutes, instead of the 15 minutes that the general population are recommended to wait.

The CDC published information about allergic reactions that caused anaphylaxis after almost 2 million doses of the Pfizer vaccine were given. They estimate that about 30% of the population has allergies. However, only 21 anaphylactic allergic reactions occurred in those 2 million vaccine recipients. Of these 21 people, 17 of 21 had previously identified allergies, but 4 of 21 had no previously identified allergies at all. Of those who had allergies, no significant pattern emerged, suggesting that there is not a causal association between allergies (or specific allergies) and an anaphylactic reaction to the vaccine. Further, since millions more doses have been administered, this rate of allergic reaction has not continued, suggesting that the likelihood of having an allergic reaction following receipt of the COVID-19 vaccine is not likely to differ from background rates.

If a person with history of allergies continues to have concerns about whether or not it is safe to get the COVID-19 vaccine, they should contact their primary care provider or allergist, who has the benefit of their complete medical history and will, therefore, be in the best position to discuss any potential risks and benefits for that individual.

Last updated: 5/27/2021

How well does the COVID-19 vaccine work in adolescents?

The clinical trial measured two things to evaluate how the vaccine worked:

  1. Disease – While 18 participants (12-15 years of age) in the placebo group got COVID-19 at least seven days after having the second dose of the vaccine, none in the vaccinated group were infected. This represents 100% efficacy.
  2. Immune response – Now that we know what antibody levels adults experience following vaccination, studies can compare the levels in other groups to see if the vaccine works as well. These are often referred to as “non-inferiority studies,” meaning the vaccine is being tested in the study group to make sure it works at least as it does in another group previously studied. In the Pfizer study, average neutralizing antibody responses were more than 1.5 times higher in 12- to 15-year-olds compared with older children and young adults. While we still do not know if a certain level of virus-neutralizing antibodies indicates that an individual is protected against infection, we can be confident that vaccinated teens respond equally well, if not better than, adults.

Last updated: May 13, 2021

Why do kids need the COVID-19 vaccine since they don’t get that sick if they are infected?

While children and teens may not be as likely to get severely ill from COVID-19, it can still happen and, in fact, the average age of hospitalizations has been decreasing, particularly since the oldest members of our communities have been vaccinated. With this in mind, parents and teens should consider the following:

  • In the first 13 months of the pandemic, more than 1.5 million 12- to 17-year-olds have been knowingly infected. This number is an under-representation given that many people may not have symptoms or be sick enough to get tested or seek medical care.
  • In April 2021, about 9% of those diagnosed with COVID-19 were 12 to 17 years old.
  • Hospitalization rates among this age group have also been increasing. More than 13,000 12- to 17-year-olds were hospitalized with COVID-19 by early May 2021, and, in fact, more teens have been hospitalized with COVID-19 than were hospitalized with H1N1 during the 2009-2010 influenza pandemic.
  • Conditions such as obesity, asthma, and developmental delay, as well as other pre-existing conditions, increase the chance for hospitalization.
  • As of late July 2021, about 350 children and teens up to 17 years of age have died from COVID-19.
  • As of the end of June 2021, about 4,200 cases of multisystem inflammatory syndrome in children (MIS-C) have been diagnosed and 37 deaths occurred. About 2 in 3 of these occurred in 5- to 14-year-olds. MIS-C typically occurs 2 to 6 weeks after having COVID-19, can occur following a mild infection, tends to be more severe in adolescents and teens, and causes about 6 or 7 of every 10 individuals to be placed in intensive care. MIS-C can also affect heart function.
  • Finally, this age group can also transmit the infection to more vulnerable family and community members, such as those who are unable to get the vaccine.

Last updated: July 26, 2021

Can the COVID-19 vaccine affect puberty or fertility in my child?

No, the rumors related to COVID-19 vaccines affecting puberty or fertility are unfounded. The mRNA vaccines are processed near the injection site and activated immune system cells travel through the lymph system to nearby lymph nodes. In this manner, they are not affecting hormone levels, nor are they traveling throughout the body to other parts of the body. As such, there would not be a biological reason to expect that maturation or reproductive functionality of either males or females would be negatively affected by COVID-19 vaccination now or in years to follow.

Watch this short video in which Dr. Paul Offit discusses COVID-19, the vaccines and infertility.

You can read more about fertility and COVID-19 vaccines in this Vaccine Update article.

Last updated: May 25, 2021

If I got a COVID-19 vaccine in another country, can I get one in the U.S.?

For individuals vaccinated in another country, they may or may not be recommended to get a COVID-19 vaccine in the U.S. based on the situation:

  • If you received the recommended number of doses of a U.S.-approved vaccine (2 doses Pfizer, 2 doses Moderna, or 1 dose of J&J/Janssen), you are considered fully vaccinated and do not need additional doses.
  • If you received the recommended number of doses of a WHO-approved vaccine, you do not need additional doses.
  • If you started, but did not finish a WHO-approved vaccine, you can get the recommended doses of a U.S.-approved vaccine as long as at least 28 days have passed since your previous dose.
  • If you got a vaccine that is not FDA- or WHO-approved, you can get the recommended number of doses of a U.S.-approved vaccine at least 28 days after your most recent dose of the non-approved vaccine.

If you get a second type of vaccine, it is important to be aware that we do not have data regarding how the vaccines might interact, which is why the CDC recommends at least 28 days between doses.

Last updated: May 13, 2021

What do you know about the halt on the J&J vaccine?

Federal health officials recommended a pause on the Johnson & Johnson (J&J) COVID-19 vaccine after six women developed blood clots in their brain up to 3 weeks after their vaccine. The blood clots in the brain are called cerebral venous sinus thrombosis (CVST). While a few of these women had an underlying health condition, no pattern of pre-existing conditions emerged. These cases are similar to those caused in European countries by the AstraZeneca (AZ) vaccine, which is not currently used in the United States. The J&J and AZ vaccines are similar in that both use an adenovirus vector to induce immunity to the SARS-C0V-2 surface protein, but they use different adenovirus vectors. The J&J vaccine uses a human adenovirus, and the AZ version uses a chimp adenovirus.

The pause was recommended for three reasons:

  • First, the FDA and CDC needed time to review these cases and collect as much information as they could to figure out what was happening.
  • Second, they needed to update healthcare providers across the country on what to watch for in their patients. In this way, physicians can properly diagnose and treat the condition. This condition is very rare and treating it with blood thinners could make this situation worse.
  • Third, the pause allowed for the public to quickly become aware of the potential side effect, so that people who got the vaccine and those around them would be more likely to recognize the need to seek medical attention if they experience symptoms.

After evaluating all available sources of information, including the scientific literature, other types of clotting events in vaccine recipients, U.S.-based safety systems and European safety data, the CDC determined that the benefits of the J&J/Janssen vaccine clearly and definitively outweigh the risks.

As of early May 2021, individuals should be aware of the following:

  1. Twenty-eight cases occurred after nearly 9 million people received the J&J vaccine, so the risk is extremely low, about 3 in a million. Twenty-two cases have occurred in women and 6 cases have occurred in males.
  2. The cases occurred in individuals between 18 and 64 years of age; however, women between 30 and 49 years of age are at the highest risk of experiencing this severe side effect. To date, three people have died from this side effect.
  3. Most cases have occurred between 1 and 2 weeks after vaccination, but some have been identified as early as 3 days and as late as 15 days following vaccination. Therefore, anyone who gets the J&J vaccine should monitor for symptoms up to 3 weeks after getting vaccinated.
  4. This episode demonstrates the robustness of the vaccine safety monitoring systems in place in the U.S. as the systems detected something happening at a rate of about 1 in a million in less than 6 weeks.

No cases of this condition have been identified following receipt of either mRNA vaccine. At this time almost 250 million doses of the two mRNA vaccines have been administered in the U.S.

Watch this short video in which Dr. Offit discusses the differences between typical blood clots and those occasionally reported following receipt of the COVID-19 adenovirus-based vaccine.

Last updated: 5/13/2021

What should I do if I had the J&J vaccine?

If you had the J&J vaccine more than 3 weeks ago, you are extremely unlikely to experience either thrombosis with thrombocytopenia syndrome (TTS) or Guillain-Barré syndrome (GBS).

If you had the J&J vaccine within the last 3 weeks, although the risk is low, you should still monitor yourself for unusual symptoms, including severe headache, severe abdominal pain, unexplained leg pain, or shortness of breath, which may result from TTS, or muscle weakness or paralysis, which may result from GBS. If you develop unusual symptoms, you should seek medical attention and be certain to tell the healthcare provider the date you received the J&J vaccine. For TTS, the physician can very quickly determine whether your problem is related to the vaccine by performing a simple complete blood count. If the platelet count is extremely low, the symptoms might be related to the vaccine. We would also recommend registering for v-safe, the CDC’s vaccine monitoring system if you have not done so already.

Last updated: 7/26/21

Should I stop using my birth control if I got the J&J vaccine?

It is not necessary to stop taking birth control pills. Individuals affected by thrombotic thrombocytopenic syndrome (TTS), which is an unusual combination of low platelet count (thrombocytopenia) and clotting (thrombosis) did not share common medical histories, such as use of birth control pills; therefore, stopping usage would not change your risk for TTS.

Last updated: 4/23/21

What are CVST and thrombocytopenia?

Cerebral venous sinus thrombosis (CVST) is a condition that causes blood clots in large vessels that drain blood from the brain. Although it is uncommon, the condition more often affects women between 20 and 50 years of age.

Thrombocytopenia is low numbers of cells called platelets. Platelets are cells that help our blood clot. When a person has this condition, they are at risk for bleeding since their body lacks the ability to efficiently stop the bleeding.

It is very uncommon for CVST and thrombocytopenia to occur at the same time, which is what makes this diagnosis following receipt of the J&J vaccine so unusual. Likewise, the clots have not just occurred in the large vessels near the brain in some of the affected individuals.

Watch this short video in which Dr. Offit discusses the differences between typical blood clots and those occasionally reported following receipt of the COVID-19 adenovirus-based vaccine.

Last updated: 4/16/21

What is the difference between TTS and CVST?

Thrombosis with thrombocytopenia syndrome, or TTS, is the name that has been given to the condition identified in a small number of individuals after receipt of the COVID-19 J&J/Janssen or AstraZeneca vaccines. TTS is distinct from cerebral venous sinus thrombosis, or CVST, because in TTS not all of the clots are associated with the large vessels of the brain. Some individuals had clots in their lungs, heart, intestines, spleen, or large blood vessels in their legs. However, CVST was originally used, and may still be used to refer to the condition by some individuals, because the original cases closely resembled this previously defined condition.

Watch this short video in which Dr. Offit discusses the differences between typical blood clots and those occasionally reported following receipt of the COVID-19 adenovirus-based vaccine.

For more information about TTS, watch this short animation from the Melbourne Vaccine Education Centre.

Last updated: 7/6/21

Are some people at higher risk of having the clotting after the J&J vaccine?

In the U.S. women between 30 and 49 years of age have most often been affected by this condition compared with other groups; however, both men and women between 18 to 64 years of age have been affected.

Data regarding the race of all affected in the U.S. have not been shared, but at the time of the pause, those which were known were White. With this said, a large percentage of the recipients of the J&J vaccine at the time of the pause had also been White (about 63%), so there is no reason to think that people of other races would be exempt from this side effect.

Last updated: 5/13/2021

Could the mRNA vaccines from Pfizer and Moderna cause the same clotting problem as the J&J vaccine did?

The Johnson & Johnson (J&J)/Janssen COVID-19 vaccine is an adenovirus vector vaccine, which is different from the Pfizer and Moderna mRNA vaccines. At the time of the J&J/Janssen pause, more than 182 million doses of the mRNA vaccines had been administered and no cases of thrombosis with thrombocytopenia syndrome, or TTS, had been reported. Three people out of about 85 million doses of Moderna had blood clots, but they did not have low platelets. The number of blood clots experienced by those who got the Moderna vaccine would be expected based on the background rate of clotting in the general population.

Last updated: 5/13/2021

Can I get the COVID-19 vaccine during my menstrual cycle?

Yes. Women do not need to schedule their COVID-19 vaccine around their menstrual cycle:

  • The immune system is not sufficiently compromised by either the COVID-19 vaccine or the menstrual cycle that scheduling them around one another would be of benefit. Indeed, delaying vaccination around a woman’s cycle may only leave her unprotected from COVID-19 for a longer time without offering any known benefit.
  • The mRNA and adenovirus vaccines are processed in immune system cells near the injection site and then those cells travel through the lymph system to nearby lymph nodes, where additional cells of the immune system are activated. As such, the vaccines would not be expected to affect the menstrual cycle. If a woman experiences a delayed cycle following vaccination, one possible explanation could be hormonal changes caused by stress, which in turn can affect a woman’s cycle. However, women with concerns should speak with their doctor since cycles can be delayed for other reasons as well. 
  • The COVID-19 vaccine is not shed after vaccination, so being around recently vaccinated individuals would not be expected to affect someone’s cycle.

You can read more about menstruation and COVID-19 vaccines in this Vaccine Update article.

Last updated: 5/25/2021

Do the COVID-19 vaccines contain live virus?

Neither the mRNA (Moderna and Pfizer) nor adenovirus (J&J/Janssen and AstraZeneca) vaccines contain live virus. Each of these contain a single gene from the virus that causes COVID-19. The gene instructs our cells to make the protein, but no other proteins from the virus are made, so the whole virus particles are never present. In this manner, people who were vaccinated cannot shed, or spread, the virus to other people.

Last updated 4/23/2021

Do the COVID-19 vaccines cause viral shedding?

Viral shedding occurs when a person is infected with a virus and whole viral particles produced during the infection are transmitted in the individual’s secretions. For viruses that infect the respiratory tract, these particles are often found in secretions from the nose and mouth, such as saliva or mucus.

Some people wonder whether they can shed the virus as a result of vaccination. In the case of mRNA and adenovirus-based vaccines approved for use in the U.S., the short answer is no. Both of these types of vaccines only introduce a single protein from the virus that causes COVID-19 – the spike protein. As such, whole viral particles are never produced during vaccine processing. Indeed, people are not considered to be infected when they are vaccinated because the virus does not replicate in them. Further, the vaccines are processed near the site of injection, so the spike protein produced during processing would not be found in nasal or oral secretions. As such, they cannot “shed” the single protein either.

While people who are vaccinated are less likely to be infected, there is a still a small chance that the virus could replicate at low levels in the nasal or oral cavity before the immune system stops it. If this happens, the individual may be able to shed the virus produced during the brief period of replication.

Read more about viral shedding in this Parents PACK article, “Viral Shedding and COVID-19 — What Can and Can’t Happen."

Last updated: June 14, 2021

How do mRNA vaccines work?

People make mRNA all the time. In our cells, DNA in the nucleus is used to make mRNA, which is sent to the cytoplasm where it serves as a blueprint to make proteins. Most of the time, the proteins that are produced are needed to help our bodies function.

mRNA vaccines take advantage of this process by introducing the mRNA for an important protein from the virus that the vaccine is trying to protect against. In the case of COVID-19, the important protein is the spike protein of the SARS-CoV-2 virus. The mRNA that codes for the SARS-CoV-2 spike protein is taken up by cells called dendritic cells, which express the spike protein on the cell surface, travel to a local lymph node, and stimulate other cells of the immune system (B cells) to make antibodies. These antibodies protect us, so that if we are exposed to SARS-CoV-2 in the future, our immune system is ready and we don’t get sick.

The vaccine is processed over a 1- to 2-week period after vaccination during which time the immune response develops. However, the mRNA only directs protein production in the cell for 1 to 3 days before it breaks down. Once it breaks down, the cell stops making the spike protein.

Last updated 7/29/2021

How do adenovirus vector vaccines work?

Adenovirus vector vaccines take advantage of a class of relatively harmless viruses, called adenoviruses. Some adenoviruses cause the common cold, but others can infect people without causing illness. To use these viruses for vaccine delivery, scientists choose types of adenovirus that do not cause illness and to which most people have not been exposed. They alter the virus by removing two of the genes that enable adenovirus to replicate in people, and they replace one of those genes with the one for the SARS-CoV-2 spike protein.

Like human cells, adenoviruses contain DNA as their genetic material. So, when an adenovirus vaccine is administered, it enters cells of the immune system called dendritic cells where it releases the DNA that includes the gene for the spike protein, and the genetic material enters the nucleus of the cell. In the nucleus, the DNA is used to make messenger RNA (mRNA), which is released into the cytoplasm to serve as a blueprint for making proteins. The DNA from the viral vector, however, cannot insert into the cell’s DNA. The mRNA causes the SARS-CoV-2 protein to be produced. The dendritic cells puts pieces of the SARS-CoV-2 spike protein on their surface and travel to a draining lymph node where they stimulate other cells of the immune system; specifically, B cells that make antibodies, T cells that help B cells make antibodies, and other T cells that can kill virus-infected cells. Antibodies against the spike protein will now prevent the virus from causing an infection in the future.

Find out more about adenovirus vaccines in this Vaccine Update article, “Getting Familiar with COVID-19 Adenovirus-replication-deficient Vaccines.”

Last updated: 3/1/2021

How did the vaccine companies (e.g., Pfizer and Moderna) decide which mRNA to use?

In order for a virus to reproduce and cause infection, it must get into cells and take over the cellular machinery. Because viruses attach to cells using a particular protein on their surface, in this case the SARS-CoV-2 spike protein, scientists understood that blocking that attachment would be a direct way to prevent infection. One way to block this attachment is with antibodies that bind to the surface protein. As such, when the genome was published, scientists developing the nucleic acid or protein subunit vaccines (i.e., those that only used part of the virus) chose the gene for the spike protein, anticipating that this would be the most direct route to developing an effective vaccine.

Last updated: 3/31/2021

Who should NOT get the COVID-19 vaccine?

Most people are able to get COVID-19 vaccine. But, a few groups of people either should not get the vaccine or should get a particular version. Likewise, some individuals should consult with their doctor or follow special procedures.

People who should NOT get any COVID-19 vaccine:

  • Those younger than 12 years of age
  • People currently isolating or experiencing symptoms of COVID-19; these people can get vaccinated once they are finished isolation and their primary symptoms have resolved.

People who cannot get the mRNA vaccine (Pfizer or Moderna), but may be able to get the J&J/Janssen vaccine:

  • Anyone with a previous severe or immediate allergic reaction (i.e., one that causes anaphylaxis or requires medical intervention) to a COVID-19 mRNA vaccine dose or an mRNA vaccine component.
  • Anyone with a known allergy to polyethylene glycol

People who cannot get the adenovirus vaccine (J&J/Janssen), but may be able to get the mRNA vaccine (Pfizer or Moderna):

  • Anyone with a previous severe or immediate allergic reaction (i.e., one that causes anaphylaxis or requires medical intervention) to the COVID-19 adenovirus vaccine or one of its components
  • Anyone with a known polysorbate allergy
  • Those 12-18 years of age can get the Pfizer mRNA vaccine, but not other versions (as long as they do not have other contraindications that prevent receipt of the vaccine).

People who may get the vaccine after considering risks and benefits and/or consulting with their healthcare provider:

  • Individuals with a history of severe or immediate allergic reaction to any vaccine or injectable medication (These individuals should be observed for 30 minutes after receipt of the vaccine.)
  • People who have a severe or immediate allergic reaction to one of the types of vaccines and for whom the cause of the reaction is unknown (i.e., which component caused the reaction) should consult an allergist or immunologist to determine whether the individual can get the other version. If they proceed, they should be vaccinated at a location with medical facilities and staff prepared to respond to medical emergencies.
  • Pregnant women
  • People with certain immune-compromising conditions
  • Breastfeeding women
  • People on anticoagulants

People who should follow special procedures

  • Someone with a history of severe or immediate allergic reaction (requiring medical intervention) to anything other than a vaccine or injectable medication can get the vaccine, but they should remain at the vaccination location for medical observation for 30 minutes after receipt of the vaccine.
  • Pregnant women who develop a fever after vaccination should take acetaminophen. (See more in the pregnancy-related questions lower on this page.)
  • People who recently had COVID-19 and were treated with antibody-based therapies (e.g., monoclonal antibodies or convalescent plasma) should wait until 90 days after treatment to be vaccinated.
  • Children (C) or adults (A) diagnosed with multisystem inflammatory syndrome (MIS-C or MIS-A) should delay vaccination until they recover and at least 90 days have passed from their diagnosis of this condition.
  • People with a known COVID-19 exposure should wait until their quarantine is over before getting vaccinated (unless they live in a group setting, such as a nursing home, correctional facility, or homeless shelter, in which case they can be vaccinated during the quarantine period).

Last updated 5/13/2021

Where can I get the vaccine?

States have lifted their eligibility restrictions, but each state has slightly different approaches to distribution. As such, we suggest checking your state health department website. We also recommend checking for vaccine at local pharmacies, healthcare facilities, mass vaccination sites or mobile clinics.

You can find your state’s information about COVID-19 vaccine distribution using this information prepared by our colleagues at Vaccinate Your Family.

Last updated: 4/23/2021

What are the side effects of the COVID-19 vaccine?

Side effects from both the mRNA and adenovirus vaccines are caused as part of the immune response to the vaccine.

The most common side effects from the mRNA vaccines (Pfizer and Moderna) are:

  • Fatigue
  • Headache
  • Muscle aches

Side effects occurred during the first week after vaccination but were most likely one or two days after receipt of the vaccine. Side effects were more frequent following the second dose and more likely to be experienced by younger, rather than older, recipients. Although most people will not have significant side effects, some people may wish to schedule their vaccination, so that they will not need to call out of work the next day if they don’t feel well.

A small number of young adults, particularly males, who got the mRNA vaccine experienced mild, short-lived inflammation of the heart, called myocarditis. This condition tends to occur within 4 days of receipt of the second dose. Recently vaccinated individuals who experience chest pain or shortness of breath should seek medical care. This condition tends to resolve within 2-3 weeks and does not cause long-term heart damage.

The most common side effects from the adenovirus vaccine (Johnson & Johnson/Janssen) are:

  • Injection site pain and less often redness or swelling
  • Headache
  • Fatigue
  • Muscle aches
  • Fever

Side effects occurred during the first seven to eight days after vaccination but were most likely to occur one or two days after receipt of the vaccine. Side effects were more often experienced by younger, rather than older vaccine recipients.

Two rare, but potentially dangerous conditions, have been identified following receipt of the adenovirus-based vaccines, such as the J&J/Janssen version:

  • Thrombosis with thrombocytopenia syndrome, or TTS, occurs in about 3 of every 1 million vaccine recipients and develops up to 3 weeks after getting vaccinated. Individuals between 18 and 64 years of age, both female and male, who got the J&J/Janssen vaccine have experienced this condition; however, women between the ages of 30 and 49 years of age are at the greatest risk. Anyone who got the J&J/Janssen vaccine less than 3 weeks ago should seek medical care if they develop severe headache, shortness of breath, severe abdominal pain, unexplained leg pain, easy bruising, or small red spots on the skin. Anyone seeking medical care with one or more of these symptoms should mention their recent receipt of the vaccine, so healthcare providers can order the appropriate diagnostic tests and treatments.
  • Guillain-Barré syndrome, or GBS, occurs in about 1 of every 120,000 vaccine recipients, most often during the first 3 weeks after getting vaccinated. The condition has most often been identified in males younger than 65 years of age, but it can occur in females and those older than 65 years on occasion. While rare, most cases have required hospitalization and, to date, one person has died. Anyone who recently received an adenovirus-based COVID-19 vaccine and experiences muscle weakness or paralysis should seek medical treatment and inform the healthcare provider of the recent vaccination. It should also be noted that COVID-19 has also been associated with GBS; so, natural infection with SARS-CoV-2 also appears to be a rare cause of GBS.

Last updated: July 26, 2021

Can I take medicine for the side effects after I get the vaccine?

The CDC has indicated that you can take anti-fever or anti-inflammatory medications if necessary following COVID-19 vaccination, but it is important to know that doing so could diminish the level of immunity that develops. This is true anytime you take these types of medications, whether following vaccination or to treat illness. Generally speaking, the “symptoms” people experience following vaccination or during illness, such as fever, redness, or fatigue, are caused by your immune system responding. For example, fever is your body turning up its “thermostat” to make the immune system more efficient and the pathogen less efficient. For these reasons, if you are not very uncomfortable, it is better not to take these medications.

Some wonder how long they should wait after vaccination before taking these types of medicines, so their immune response is not affected. As a rule of thumb, the immune response for the mRNA vaccines develop over a week or two after vaccination and for the adenovirus vaccines over the course of about four weeks, but the greatest chance of affecting your immune response would be in the first few days after receipt of the vaccine. Indeed, in the adenovirus vaccine studies, about 1 in 4 vaccine recipients took fever-reducing medication (antipyretics), and most people were still protected from severe disease and all were protected against hospitalization.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 3/1/2021

If I don’t have side effects, does that mean the vaccine did not work?

Many people will get the vaccine and not experience side effects. This does not mean that the vaccine did not work for them. In the clinical trials side effects occurred at varying rates, for example only about 1 to 20 of every 100 people who received the mRNA vaccine had a fever, but we know that the mRNA vaccine worked for more than 90 of every 100 people.

Last updated: 3/1/2021

What are the expected long-term side effects of the vaccination for COVID-19?

  • Most negative effects occur within 6 weeks of receiving a vaccine, which is why the FDA asked the companies to provide 8 weeks of safety data after the last dose.
  • mRNA vaccines: The mRNA in the vaccine breaks down pretty quickly because our cells need a way to stop mRNA from making too many proteins or too much protein. But, even if for some reason our cells did not breakdown the vaccine mRNA, the mRNA stops making the protein within about a week, regardless of the body’s immune response to the protein.

    Read more about COVID-19 mRNA vaccines in this Parents PACK article, “Long-term Side Effects of COVID-19 Vaccine? What We Know.”

    Watch a short video of Dr. Paul Offit explaining why COVID-19 vaccines would not be expected to cause long-term side effects.
  • Adenovirus-based vaccines: Although the DNA from adenovirus-based vaccines does not break down as quickly as mRNA, the DNA cannot alter our DNA because a gene for the enzyme, integrase, is not present.

Last updated: 3/1/2021

Should I stop taking my daily dose of aspirin before getting the COVID-19 vaccine?

If your daily dose of aspirin was prescribed by your physician following a stroke or heart attack, we recommend speaking to that doctor about whether to stop taking your medication for a day or two prior to vaccination. If, however, your daily dose of aspirin is because you have risk factors for a stroke or heart attack (such as high blood pressure or high levels of “bad” cholesterol) but have never had a stroke or heart attack, you should consider discontinuing the aspirin not only prior to your COVID-19 vaccine, but all together. The data show that while daily aspirin helps prevent second strokes or heart attacks, it does not help prevent first occurrences, even in people who are at increased risk. Our director, Dr. Paul Offit, carefully reviewed the data related to this topic for his book, Overkill: When Modern Medicine Goes Too Far.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 2/1/2021

What should I do if I took pain medicine before getting the COVID-19 vaccine?

While your initial immune response may have been lower, you will likely still have developed some immunity. Even if your immune response is somewhat lower overall, you are likely to develop sufficient levels of immunity to reduce your chance for infection. In addition, even if you were infected, you would be likely to experience disease that is less severe and of shorter duration.

Last updated: 3/1/2021

What if I can’t get the second dose 21 (Pfizer) or 28 (Moderna) days after the first dose?

The Centers for Disease Control and Prevention (CDC) allows for a 4-day grace period when assessing on-time receipt. This means the following ranges of days are considered “on-time” for receipt of the second dose:

  • Pfizer vaccine: 17 to 25 days after the first dose
  • Moderna vaccine: 24 to 32 days after the first dose

People should try to get the second dose during this period or as soon after as possible. However, if your second dose is given later than this, you do not need to restart the vaccine. You still only need to get the second dose. However, it is important to note that the first dose did not protect as many people as were protected after the second dose, so if you are exposed to SARS-CoV-2 during the delay, you may or may not have enough immunity to prevent you from experiencing symptoms.

Last updated: 1/19/2021

What is the difference between the first and second dose of the COVID-19 mRNA vaccine?

In the United States, the ingredients in the vial for dose 1 and dose 2 of the same brand are exactly the same. When people talk about dose 1 doses and dose 2 doses, they are just talking about vaccine supply. If you arrive for dose 1 and the person behind you is getting dose 2, they can come out of the same vial.

One vaccine used in some other countries, Sputnik V, has different components in dose 1 and dose 2. Both are adenovirus vector vaccines, but dose 1 uses adenovirus 26 (Ad26) and dose 2 uses adenovirus 5 (Ad5).

Last updated: 3/1/2021

Can I get the second dose of COVID-19 mRNA vaccine in my other arm?

Yes. It is okay to get the second dose in the other arm as the immunity generated by the first dose will be circulating in your body watching for a potential exposure.

Indeed, individuals who experience a delayed reaction at the injection site (a rash that develops a few days to a couple of weeks after receipt of the vaccine) are recommended to get the second dose in the opposite arm.

Last updated: 3/1/2021

Can my second dose of the COVID-19 mRNA vaccine be from a different company?

The CDC has recommended that people get the same version because that is what the data in the clinical trials were based on. However, they have indicated that “in exceptional circumstances” if the same version is not available, a person can, for example, get the Pfizer vaccine first and the Moderna vaccine second. The two doses should be separated by at least 28 days if different brands are used. However, people who got the first dose of an mRNA vaccine should not switch to the adenovirus version (Johnson & Johnson/Janssen). The best-case scenario would be that most people will be able to get the second dose from the same vaccine maker as their first dose.

Last updated: 3/1/2021

Is it okay for people in the same house to get different types of COVID-19 vaccine or should they get the same brand?

It is fine for people in the same home to get different brands or versions of COVID-19 vaccine.

Last updated: 3/18/21

How long do I need to wait if I had or need to get a non-COVID-19 vaccine?

The Centers for Disease Control and Prevention (CDC) has updated their recommendations, so that individuals do not need to delay between receipt of COVID-19 vaccine and other vaccines.

Watch this short video in which Dr. Hank Bernstein explains the benefits of receiving routine vaccines at the same time as the COVID-19 vaccine.

Last updated: 5/13/2021

Are young children susceptible to COVID-19, especially if a parent tests positive?

While younger children do not appear to be as easily infected with SARS-CoV-2, they can still be infected. Therefore, if a parent tests positive, they should still try to isolate from other members of the household, and all others in the home, including any children, should quarantine and be monitored for symptoms, as per CDC recommendations for exposure. The CDC has a dedicated page with guidance for situations in which a parent tests positive.

Likewise, even after parents are vaccinated, they should be aware that their children could be infected and follow public health guidance to ensure that the children are not inadvertently exposed to the virus.

Last updated: 4/23/2021

What is multisystem inflammatory syndrome (MIS-C or MIS-A)?

Multisystem inflammatory syndrome can occur in children (MIS-C) or adults (MIS-A). Development of symptoms typically occurs a few weeks after SARS-CoV-2 infection and can occur even in those who did not experience symptoms of COVID-19. Often multiple organs and body systems are involved, including effects on the gastrointestinal tract, heart, kidneys, skin, lungs, and eyes. Individuals with unexplained rash, vomiting or diarrhea, shortness of breath or chest pain or palpitations should seek medical care. Some people with MIS-C or MIS-A will require admission to intensive care and a small number may require mechanical ventilation.

Watch this short video in which Dr. Offit discusses MIS-C, MIS-A, and long COVID.

Last updated: 6/16/2021

What is long COVID?

Long COVID, also known as COVID syndrome or long-term COVID, is a condition characterized by long-lasting symptoms related to previous SARS-CoV-2 infection. Symptoms can last for weeks or months after viral clearance and resolution of the initial infection. Examples of the types of symptoms that affected individuals report include fatigue, difficulty thinking or concentrating (“brain fog”), headache, loss of taste or smell, dizziness, heart palpitations, chest pain, shortness of breath, cough, joint or muscle pain, anxiety, depression, or fever. Symptoms sometimes appear or worsen after physical or mental activity. The reasons for or susceptibility to these long-lasting effects remain uncertain but are being studied.

Watch this short video in which Dr. Offit discusses MIS-C, MIS-A, and long COVID.

Last updated: 6/16/2021

Does a vaccinated person present a risk to unvaccinated family members in the same house?

Vaccinated people do not shed virus as a result of vaccination. Neither the mRNA nor the adenovirus vaccines are composed of live viruses, so there is no infectious virus to spread from a vaccinated person to someone else.

But we do not yet know if a vaccinated person who encounters the virus can still experience what is referred to as “asymptomatic infection.” An asymptomatic infection occurs when a person is exposed to the virus in the community and the virus can still replicate in their body, but they don’t have symptoms because their immune system stifles the infection as a result of vaccination. In this scenario, the person could potentially spread the virus without even knowing they are infected. While it is not anticipated that vaccinated individuals will be likely to spread the virus even if they experience asymptomatic infection, this has not yet been shown to be the case. Therefore, we need to practice caution until we know for certain.

Given that families and friends will not all be vaccinated yet, vaccinated individuals should continue to follow public health guidance when they are out in the community to decrease the chance of introducing the virus in the home through asymptomatic infection. Likewise, even when a whole family is vaccinated, continuing to practice these measures will be important for two reasons:
1. The vaccine will not work for everyone, so someone in the home who has been vaccinated may still be susceptible.

2. People outside of the family’s “bubble,” like co-workers, extended family members, neighbors, and others they come into contact with, may not have been vaccinated (or may be in the group for whom the vaccine does not work).

This approach will be important until we can get control over the spread of virus. Once enough people have been vaccinated to slow the spread of the virus, we will all be able to move away from these public health measures.

Read more in the January 2021 Parents PACK newsletter article, “When the Whole Family Has Not Yet Been Vaccinated Against COVID-19.”

Last updated: 4/23/2021

What ingredients are in the COVID-19 mRNA vaccine?

The mRNA vaccines include:

  • mRNA – This mRNA is for the spike protein of SARS-CoV-2, the virus that causes COVID-19.
  • Lipids - These are molecules that are not able to dissolve in water. They protect the mRNA, so that it does not break down before it gets into our cells. These can be thought of as little “bubbles of fat,” which surround the mRNA like a protective wall. There are four different lipids in the Pfizer vaccine and three in the Moderna vaccine. One of the lipids in both vaccines is cholesterol. The lipids are the most likely components of the vaccine to cause allergic reactions.
  • Salts and amines - The Pfizer vaccine contains four salts. One is table salt. The salts are used to keep the pH of the vaccine similar to that found in the body, so that the vaccine does not damage cells when it is administered. The Moderna vaccine also contains four chemicals to balance the pH, but two are in a class of organic compounds known as “amines” and two are acetic acid and its salt form, sodium acetate. Acetic acid is the main component of vinegar (other than water).
  • Sugar – This ingredient is literally the same as that which you put in your coffee or on your cereal. It is used in both of the vaccines to help keep the “bubbles of fat” from sticking to each other or to the sides of the vaccine vial.

These are the only ingredients in the mRNA vaccines.

NOT in the COVID-19 mRNA vaccines:

The CDC has the list of specific lipids and salts posted on its website.

Watch this short video in which Dr. Paul Offit talks about the ingredients of COVID-19 mRNA vaccines.

Last updated 2/19/2021

What ingredients are in the COVID-19 adenovirus-based vaccine?

The adenovirus vaccine includes:

  • Adenovirus type 26 (Ad26) containing SARS-CoV-2 spike protein gene and altered so that it cannot replicate
  • Stabilizers – Salts, alcohols, polysorbate 80, and hydrochloric acid
  • Manufacturing by-products – amino acids

NOT in the COVID-19 adenovirus vaccines:

  • Animal Products
  • Antibiotics
  • Blood products
  • Egg Proteins
  • Gluten
  • Microchips
  • Pork products
  • Preservatives, like thimerosal
  • Soy

Last updated: 3/4/2021

Do COVID-19 vaccines contain antibiotics?

No. Neither the mRNA vaccines (Pfizer and Moderna) nor the adenovirus vaccine (Johnson & Johnson/Janssen) contain antibiotics.

Watch this short video in which Dr. Hank Bernstein discusses which ingredients are and are not in the COVID-19 mRNA vaccines.

Last updated: 3/1/21

Can mRNA vaccines change the DNA of a person?

Since mRNA is active only in a cell’s cytoplasm and DNA is located in the nucleus, mRNA vaccines do not operate in the same cellular compartment that DNA is located.

Further, mRNA is quite unstable and remains in the cell cytoplasm for only a limited time (See “What stops the body from continuing to produce the COVID-19 spike protein after getting an mRNA vaccine?” below.) mRNA never enters the nucleus where the DNA is located so it can’t alter DNA.

Watch this short video in which Dr. Paul Offit explains why it’s not possible for mRNA vaccines to alter a person’s DNA.

Last updated 12/15/2020

Can adenovirus-based vaccines change the DNA of a person?

Adenovirus-based vaccines contain DNA, which enters the nucleus of cells after vaccination, but the virus cannot replicate and the vaccine does not include a necessary enzyme, called integrase. Therefore, the vaccine cannot change a person’s DNA.

Last updated: 3/1/2021

What stops the body from continuing to produce the COVID-19 spike protein after getting a COVID-19 mRNA or adenovirus- based vaccine?

Both vaccines result in production of spike protein that results from mRNA blueprints. Because our cells are continuously producing proteins, they need a way to ensure that too many proteins do not accumulate in the cell. So, generally speaking, mRNA is always broken down fairly quickly. Even if for some reason our cells did not breakdown the vaccine mRNA, the mRNA stops making the protein within about a week, regardless of the body’s immune response to the protein. Once the mRNA is broken down, the blueprint is gone, so the cell can no longer continue to make spike proteins.

Likewise, while the adenovirus-based vaccine delivers DNA and the DNA lasts longer than mRNA, studies have shown that adenovirus-based DNA does not last longer than a few weeks.

Watch this short video in which Dr. Hank Bernstein explains how the mRNA from the COVID-19 vaccine is broken down and removed from the body.

Last updated 4/23/2021

Will the spike protein from current vaccines cause an issue if there are future variants?

This question has two aspects – longevity of the spike protein and effects of current immune responses to future variants. While related, these are not cumulative issues, meaning they involve separate considerations:

  • Longevity of the spike protein - The spike protein does not remain in the body for an extended time, nor does it travel around the body. The only thing that remains after the vaccine is processed are antibodies and memory immune cells that will recognize the virus if we are exposed in the future. The antibodies and memory cells will or will not recognize the variant spike protein. If they do, great – we will have some protection. If they don’t, it will be just like an antibody to flu or measles, it will have no effect.
  • Effects of current immune responses to future variants - As the virus evolves, it changes, so we might find ourselves dealing with different versions of the virus in the future. Current variants have not changed significantly enough that our antibodies have stopped being protective, so for now, we do not need additional doses of vaccine. If, however, one (or more) of these variants changes enough that the vaccine-induced immunity (or disease-induced immunity) is no longer protective, we will need to make new COVID-19 vaccines that protect against the new version of the virus. As described above, in this scenario the existing immunologic memory (antibodies or memory cells) will no longer be effective, but it will not be problematic either. A new vaccine would induce new immunity and the process would begin anew.

Last updated: May 25, 2021

How well do the COVID-19 vaccines work?

All three COVID-19 vaccines approved for use in the U.S. work well.

mRNA vaccines: More than 9 of every 10 people vaccinated during the clinical trials were protected from disease. Likewise, a study of vaccine performance in the community also found that 9 of 10 individuals are protected. Read a summary of the study.

Adenovirus-related vaccine: While only about 6 or 7 of every 10 people vaccinated during the clinical trials were protected from disease, the study found that 8 or 9 were protected from severe disease and all were protected against hospitalization by one month after vaccination. Also, studies of the mRNA and adenovirus vaccines were done on different populations, making it difficult to compare these vaccines. Whereas all of the mRNA studies were done in the United States, the adenovirus vector vaccine (Johnson & Johnson/Janssen) studies were performed in Latin America, South Africa and the United States. Because the viral strains circulating in South Africa and Latin America were different from those circulating in the United States, it’s difficult to directly compare the relative efficacies.

Last updated 4/23/2021

Is it safe to get the COVID-19 vaccine if I have COVID-19?

The CDC recommends waiting until your symptoms go away and you are no longer isolating. If you happen to be infected, but don’t know because you have not yet developed symptoms or you have an infection without symptoms, the vaccine is not likely to be harmful. It would increase your body’s immune response against the virus.

Last updated 1/19/2021

Once I have been vaccinated against coronavirus, am I exempt from restrictions?

Fully vaccinated individuals (at least two weeks after the last dose in the series) should still follow public health measures in public, in groups that may have vaccinated and unvaccinated individuals, or in situations with individuals from multiple households. However, vaccinated individuals can gather with those from another home who are also vaccinated can gather without masks in their homes for meals.

Some have wondered why we still need to practice recommended public health measures as more individuals are vaccinated. Unfortunately, a large percentage of the population will need to be immune to slow or stop the spread of the virus. Two factors are important for understanding why:

  • While the vaccines appear to be highly effective at preventing disease, they might not prevent asymptomatic infection, meaning vaccine recipients might still be able to get infected, but not have symptoms and, therefore, unwittingly spread the virus. The companies are doing additional studies to better understand whether this is the case.
  • Scientists estimate that to control COVID-19, about 8 of every 10 people will need to be immune. Given that the U.S. population is more than 330 million people, this means that almost 200 million of them will need to be immune to reach this goal either from vaccination or natural infection.

For these reasons, there will still be some period of time during which other measures, such as masks, social distancing, and other public health measures, will be required to slow or stop the spread of the virus. And, because we won’t know who might still be able to be infected after vaccination or previous illness, everyone will be asked to comply. Watch Dr. Offit discuss the continued need for masks and social distancing in this short video.

Last updated 4/23/2021

Can I drink alcohol after getting the COVID-19 vaccine?

Alcohol suppresses the immune system, so it would be advisable not to drink alcoholic beverages for about 2 weeks after getting vaccinated.

Last updated: 12/31/2020

Is it okay to donate blood after getting the COVID-19 vaccine?

Giving blood after getting the COVID-19 vaccine will not diminish the resulting immune response, which mostly builds in the lymph nodes near the injection site. Likewise, the American Red Cross (ARC) does not require a delay following vaccination with the vaccines currently approved for use in the U.S.; however, individuals must know which brand of vaccine they received and show the immunization card if possible. More details about blood donation are available on the ARC website.

Last updated: 3/18/21

Are COVID-19 vaccines made in fetal cells?

The mRNA vaccines (those by Pfizer and Moderna) do not contain fetal cells.

But, the adenovirus-based vaccines, like Johnson & Johnson/Janssen’s, use cells originally isolated from fetal tissue (often referred to as fetal cells). These fetal cells are used to grow the vaccine virus.

To replicate, a virus needs to take over a cell’s machinery (See this animation); however, the adenoviruses used in these vaccines have been altered, so that they cannot replicate. So, to make virus to use as the vaccine, these altered viruses need to infect cells that have been altered in a way to allow the defective virus to reproduce. The special cells for this process were isolated decades ago from one of two terminated fetuses and later adapted for the adenovirus reproduction process. Neither of these are used to produce any existing vaccines grown in fetal cells:

  • HEK-293 — This is a kidney cell line that was isolated from a terminated fetus in 1972.
  • PER.C6 — This is a retinal cell line that was isolated from a terminated fetus in 1985.

These two cell lines have been maintained in the laboratory, and no additional fetuses are needed to produce adenovirus-vector vaccines.

In this short video, Dr. Paul Offit addresses fetal cells and COVID-19 vaccines.

Last updated 3/1/2021

How many doses of a COVID-19 vaccine will be needed?

The mRNA vaccines require two doses. For the Pfizer vaccine, doses should be separated by 21 days. For Moderna’s vaccine, doses should be separated by 28 days. The two mRNA vaccines are not interchangeable. A person should be sure they know which one they got as the first dose and be clear about when they should return for the second dose, particularly because the vaccines require both doses to have the best protection. Watch this video of Dr. Paul Offit explaining why getting the second dose of COVID-19 mRNA vaccine is so important.

The adenovirus vaccine (Johnson & Johnson/Janssen) only requires a single dose.

Last updated 3/1/2021

Will annual or booster doses of COVID-19 vaccines be needed?

We are still not certain whether people will need to get additional doses of the COVID-19 vaccine because we are still learning how long immunity lasts after:

  • Illness
  • Vaccination

Further, the increased presence of variants might affect whether or how often additional doses would be needed. This is one reason scientists are anxious to get as many people vaccinated as possible — the more the virus can replicate in people, the greater the chance that it will change in a way that allows it to spread widely — even among people who have been vaccinated. With this in mind, scientists are continuing to monitor variants and the ability of currently available vaccines to protect against them.

Watch this video in which Dr. Hank Bernstein explains why dosing recommendations may change over time.

Last updated 3/31/2021

How long will vaccine immunity last?

We are still learning how long immunity lasts after infection or vaccination. The latest information shows that:

  • Following infection people are not likely to be re-infected within 90 days of infection. However, they are working to learn more about immunity following infection. While some people have been re-infected after recovering from COVID-19, the number of people who have experienced this is small compared with the total number of people who have been infected.
  • Following vaccination with the mRNA vaccines, people are immune for at least 6 months and likely much longer. The same is likely to be true for the adenovirus-based vaccines too, but we are still waiting for data. Based on the elements of the immune response activated after vaccination with either the mRNA or adenovirus vaccines, it is likely that immunity will be long-lived. But time will tell, and if the virus changes in a way that evades immunity generated by vaccination, that would also affect the duration of protection.

Watch this short video in which Dr. Hank Bernstein addresses what is known about vaccine immunity and what we are still learning. 

Last updated 4/23/2021

If you had the virus, do you still need to get the vaccine?

People who had COVID-19 are recommended to get the vaccine after they have recovered. The vaccine trials included people who were previously infected with SARS-CoV-2, and the vaccine was found to be safe. Because we do not know how long antibodies last after infection and a small number of people have had more severe second bouts of infection, the vaccine can be beneficial in boosting a person’s existing immunity from infection.

Early data suggest that individuals who were previously infected may only need a single dose of the mRNA vaccines; however, the CDC has not changed its recommendations at this time because the data need to be confirmed in larger groups of individuals.

Watch this video of Dr. Paul Offit explaining why those infected with SARS-CoV-2 should still get the COVID-19 vaccine.

Watch this short video in which Dr. Offit discusses what is known about COVID-19 reinfection.

Last updated 4/23/2021

If a person is vaccinated against COVID-19, will they be able to spread the virus to susceptible people?

People will not spread the virus after vaccination with the mRNA or adenovirus vaccines. The vaccines do not deliver live virus nor do they cause the body to produce virus, so there is no chance for a vaccinated person to spread the vaccine virus to others, even if they have side effects.

Of note, however, we do not yet know if these vaccines prevent infection or if they only prevent disease:

  • Disease means people experience symptoms of illness.
  • Infection means that a virus can infect a person’s cells and reproduce, but the person may or may not have symptoms or be contagious.

If the COVID-19 vaccines only prevent disease, a person could be infected following an exposure and potentially spread the virus. Additional studies are underway to determine whether the vaccines prevent infection as well as disease. Scientists expect that even if someone experiences an asymptomatic infection, they will not be likely to infect others; however, we need to wait for the data to know for certain. Therefore, in situations of higher risk for exposure vaccinated people should still use masks and practice social distancing measures as recommended by the CDC.

Find out more about viral shedding in the Parents PACK article, "Viral Shedding and COVID-19 — What Can and Can’t Happen."

Last updated 4/23/2021

Could taking two different vaccines boost the effectiveness?

Currently, COVID-19 vaccines are not interchangeable. However, if a person gets one of the mRNA vaccines and the supply does not allow for them to get the second dose of the same brand, they can get the other mRNA vaccine, with the second dose at least 28 days after the first one. This should only be done in extenuating circumstances.

Additional studies are required because three scenarios can occur if a person gets vaccinated with two versions of vaccines against the same disease, particularly close in time:

  • They get a stronger immune response. An example of this was when children got inactivated polio vaccine and later got oral polio vaccine.
  • The second vaccine causes immunity that would be similar to receiving a second dose of the original vaccine. Using a different brand of hepatitis B vaccine for one or more doses would be an example of this.
  • The immune response generated by the first vaccine interferes with components of the response to the second vaccine, in some cases causing lower immunity. For example, when people got a pneumococcal polysaccharide vaccine (PPSV) followed by a pneumococcal polysaccharide vaccine with a harmless helper protein attached to it, called pneumococcal conjugate vaccine (PCV), they had lower antibody responses to one part of the PCV vaccine than people who got the two vaccines in the opposite order (PCV followed by PPSV).

For these reasons, studies will be important for determining the effects of getting a second type of COVID-19 vaccine shortly after receiving a different one. If, however, we find that COVID-19 vaccines are like influenza vaccines and we need to get vaccinated annually, concerns about switching types from one year to the next are less likely to be an issue.

Last updated 3/1/2021

Is a coronavirus vaccine necessary?

SARS-CoV-2 infections can be a minor hindrance or lead to severe disease or even death. While hygiene measures such as social distancing, handwashing, and wearing masks offer some help, the best way to stop this virus is to generate SARS-CoV-2-specific immunity. No virus has ever eliminated itself by inducing natural immunity in a large percentage of the population. Only herd immunity induced by vaccination can eliminate viruses, as has now been shown for smallpox and two of the three different types of poliovirus.

For more information, watch this short video of Dr. Paul Offit addressing “Why does it matter if I don’t get the COVID-19 vaccine?”

Last updated 12/15/2020

How long before a coronavirus vaccine takes effect?

The mRNA vaccines require two doses. While people will have some immunity after the first dose, protection will be most likely about one week after receipt of the second dose.

The adenovirus vaccine (Johnson & Johnson/Janssen) requires one dose. While people will have some immunity about two weeks after being vaccinated, protection will be more robust about one month after receipt of the vaccine.

Last updated 3/1/2021

Do the variants affect vaccine effectiveness?

Current variants circulating in the U.S. are being monitored for their ability to spread, cause more severe disease, and evade vaccines and treatments. To date, most of the changes have allowed for easier spread or had minor effects on vaccines or treatments. So far, none of the variants have changed enough that they require new vaccines; however, scientists are working on vaccines that would be able to protect against the most concerning variants in case additional doses become necessary.

Read more about why variants are concerning to scientists, why they should concern individuals, and how they are classified in this article from the April 2021 Vaccine Update for Healthcare Providers.

Watch this video in which Dr. Hank Bernstein provides more information about coronavirus mutations and the COVID-19 vaccines.

Last updated 4/23/2021

Can pregnant women get the COVID-19 vaccine?

Pregnant women were not included in the early COVID-19 vaccine studies, but some participants were either pregnant and did not know it or became pregnant during the course of the study. Likewise, tens of thousands of pregnant women have been immunized since the COVID-19 mRNA vaccines became available, and many of them are also being monitored through the CDC’s V-safe program.

With data from thousands of these women now in hand, no concerns have been identified and the vaccine works. While pregnant women and their babies will continue to be monitored, the CDC recently changed its statement about COVID-19 vaccines for pregnant women to more clearly recommend these vaccines for pregnant women.

Two factors, in addition to the vaccine data, were important for informing vaccine recommendations for pregnant women:

  • First, some pregnant women are at high risk for COVID-19 because of their jobs, such as healthcare workers, or existing health conditions.
  • Second, pregnant women are more likely to be hospitalized and be admitted to the intensive care unit with COVID-19 than women of the same age who were infected but weren’t pregnant.

All pregnant women should keep these two important points in mind:

  1. Pregnant women who get the COVID-19 vaccine should take acetaminophen if they develop a fever after vaccination, as fever during pregnancy can negatively affect a developing baby. Taking acetaminophen during pregnancy has been found to be safe.
  2. Likewise, regardless of vaccination status, pregnant women should practice recommended public health measures, particularly because of their increased risk if infected with COVID-19.

In this short video, Dr. Hank Bernstein discusses COVID-19 vaccination during pregnancy.

You can read more about pregnancy and COVID-19 vaccines in this Vaccine Update article.

Last updated 5/25/2021

Can I get the COVID-19 vaccine if I am breastfeeding?

Yes. Although women who are breastfeeding were not included in the clinical trials, current data suggest that COVID-19 is not transmitted through breast milk, so it is not expected that vaccination would cause a concern either. On the other hand, some women who are breastfeeding will be at higher risk for exposure, so they could benefit from receiving the vaccine.

In addition, women do not need to delay breastfeeding for any period of time before or after they have been vaccinated.

Babies may also benefit from antibodies or immune cells that may be introduced through breast milk after the mother is vaccinated. This is called passive immunity.

Both the Academy of Breastfeeding Medicine and the American College of Obstetricians and Gynecologists support this approach.

In this short video, Dr. Hank Bernstein discusses COVID-19 vaccination when breastfeeding.

You can read more about breastfeeding and COVID-19 vaccines in this Vaccine Update article.

Last updated 5/25/2021

Can I get the COVID-19 vaccine if I am trying to get pregnant?

Yes, women who are trying to get pregnant can get the vaccine. Likewise, if a woman finds out she is pregnant after getting the first dose, but before getting the second dose, she can still get the second dose on time.

Last updated 12/15/2020

Should I delay getting pregnant if I got the COVID-19 vaccine?

No, you do not need to delay pregnancy. But, if you become pregnant within 30 days of receiving a dose of vaccine, you should consider registering for V-safe, a mobile-app based program being offered by the CDC that is tracking the safety of COVID-19 vaccines.

Last updated 3/1/2021

Why was I told to wait a month after getting the COVID-19 vaccine before getting a mammogram?

Some people experience swelling of lymph nodes under their arm after getting the COVID-19 mRNA vaccine, which on occasion has been falsely identified as spread of breast cancer to lymph nodes. Therefore, delaying the mammogram can prevent the chance of this happening.

Last updated: 3/1/2021

Is it necessary to wait to get blood work done after getting the COVID-19 vaccine?

Generally speaking, it would be recommended to wait about a week after getting the mRNA vaccine and a few weeks after getting the adenovirus-based vaccine before getting bloodwork. However, it would be better to inquire with the healthcare provider who ordered the bloodwork as they have the benefit of knowing the reason for the bloodwork, the type of tests ordered, and the patient’s medical history. As such, they will be in the best position to offer this guidance for each individual situation.

Last updated: 3/18/21

Is the coronavirus vaccine being studied in children?

Yes. The Pfizer mRNA vaccine is now approved for use in those 12 years of age and older. Studies of the Pfizer vaccine are ongoing in those younger than 12 years of age, and the Moderna and J&J/Janssen vaccines are being studied in those younger than 18 years of age. 

It is important that COVID-19 vaccines be thoroughly tested in children before they are given in this group because we cannot assume that they will act the same way in younger children, particularly since we have seen that children are not affected in the same way by COVID-19 infections.

Watch this video in which Dr. Paul Offit discusses when can children get the COVID-19 vaccine and why they should get it.

Last updated: 5/13/2021

If I have an autoimmune or immune-compromising condition, can I be vaccinated?

People with immune-compromising conditions may get the COVID-19 vaccine as long as they are not in one of the following categories:

  • Severe allergy to a vaccine component (i.e., one that causes anaphylaxis or requires medical intervention)
  • History of severe allergy to any vaccine or injectable medication

However, it is recommended that individuals with compromised immune systems discuss their personal risks and benefits with a healthcare provider to determine whether to receive the vaccine. Data about how well the vaccine works and its safety in immune-compromised individuals are not currently available, so it is possible that these individuals could have a lower immune response to vaccination. On the other hand, persons with these conditions may also be at higher risk of severe disease due to COVID-19. Therefore, the CDC recommended that people who are immune-compromised or taking immunosuppressive medications could receive the vaccine if they wanted as long as they do not have other contraindications.

With this said, knowing the potential for a lower immune response, if someone with an immune-compromising condition decides to get vaccinated, it will be important to get both doses (if they receive the mRNA vaccine) and practice other public health measures until more is known about their protection against SARS-CoV-2, the virus that causes COVID-19.Post-licensure monitoring systems, like the Vaccine Adverse Events Reporting System (VAERS) and the Vaccine Safety Datalink (VSD), will be used to allow  for real-time monitoring of these sub-groups.

Last updated 3/1/2021

Can I get the COVID-19 vaccine if I had Guillain-Barré Syndrome (GBS)?

People with a history of Guillain-Barré Syndrome (GBS) can get the COVID-19 mRNA or adenovirus vaccine, as long as they do not have another condition that puts them among the people recommended against vaccination. While a small number of cases of GBS have been identified following receipt of the adenovirus-based COVID-19 vaccine, the cases have been rare and COVID-19 remains widespread, so the benefits still outweigh the risks.

Some people wonder if they can get the COVID-19 vaccine if they developed GBS following receipt of an influenza vaccine. Since COVID-19 and influenza (flu) vaccines are made differently, people with this history would not be expected to have an issue with COVID-19 vaccine. As such, they are still recommended to get COVID-19 vaccine.

Finally, many people are incorrectly told that if they had GBS, they cannot get a flu vaccine. However, most people with a history of GBS can get the flu vaccine. Only people who were diagnosed with GBS less than 6 weeks after receipt of influenza vaccine are considered to have a “precaution” for receipt of influenza vaccine, meaning that the patient and the healthcare provider should discuss the relative risks and benefits associated with getting the influenza vaccine. In fact, studies have shown that influenza disease presents a greater risk of GBS than influenza vaccination. Find out more about vaccines and GBS.

Last updated: 7/26/2021

Can I still get vaccinated if I have a cold?

People with mild cold-like symptoms are not prevented from getting the vaccine. However, if they are not feeling well, their symptoms just started, or their symptoms are getting worse, they may want to delay vaccination until they feel better; otherwise, they might not be able to tell effects of illness from those of the vaccine. If they are uncertain, they should speak to their doctor, who has the benefit of their medical history and will be in the best position to help them weigh the potential pros and cons.

Last updated: 3/1/2021

If I am taking anticoagulants (blood thinners), can I get the COVID-19 vaccine?

Patients on blood thinners are asked to speak with a healthcare provider because the vaccine is given intramuscularly, which increases the risk for bleeding. The vaccine itself does not increase the risk for this group of patients.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 1/25/2021

If I am currently taking antibiotics, can I get the COVID-19 vaccine?

As long as you are not still sick from your recent infection, you can get the COVID-19 mRNA or adenovirus-based vaccine even if you are taking an antibiotic. But, if you are still having symptoms, you should wait until you are feeling better, so that it is easier to tell if any new symptoms are from your infection or the vaccination.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 3/1/2021

If I am taking antivirals, can I get the COVID-19 vaccine?

You do not need to stop taking antiviral medication before vaccination. Because the mRNA and adenovirus-based vaccines does not rely on viral replication, antivirals should not affect development of the immune response. However, if you are still experiencing symptoms of the infection for which the antivirals were prescribed, you should wait until you are feeling better before getting the vaccine.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 3/1/2021

If I am taking biologics, can I get the COVID-19 vaccine?

Taking biologics, like Humira, is not a reason to forgo COVID-19 vaccination as per CDC guidelines. However, patients taking these types of medication may wish to consult with their doctor to discuss the potential risks and benefits of getting the COVID-19 vaccine, given that these types of medications are often prescribed for individuals with immune-compromising conditions. As a result, there may be other considerations related to the potential risks and benefits of vaccination.

For general information about vaccines and biologics, check out this printable Q&A sheet.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 1/25/2021

If I need a dental procedure, can I get the COVID-19 vaccine, or should I delay my procedure?

People can have dental procedures after receipt of the COVID-19 vaccine. Vaccine-induced immunity should not be affected by nitrous oxide or antibiotics that might be prescribed after the procedure.

Last updated: 1/25/2021

How long should I wait to get the COVID-19 vaccine after getting a steroid injection or vice versa?

You should speak with your doctor to determine whether the quantity of steroids that you are receiving is suppressing your immune system. If so, you should hold off on receiving vaccines until the effect of the steroids has worn off.

Find out more in this Parents PACK article, "Medications and COVID-19 Vaccines: What You Should Know."

Last updated: 1/25/2021

Does the COVID-19 vaccine cross the blood-brain barrier?

It would not be expected that the COVID-19 vaccines would cross the blood-brain barrier (BBB) for a few reasons.

mRNA vaccines:

  • Most of the protein that is made is bound to cells - The vaccine is injected into muscle, where dendritic cells in the area use the mRNA to make the COVID-19 spike protein. These dendritic cells, after making the spike protein, put the protein (not the mRNA) on the cell surface, travel to the nearest lymph node, and stimulate other cells of the immune system to make an immune response against the protein. This process is typical of our adaptive immune system, which you can find out more about in this animation.
  • The protein itself is too large to cross the BBB.

Adenovirus vaccine:

  • The virus is too large to cross the BBB.

Last updated 3/1/2021

Does the COVID-19 vaccine cause antibody-dependent enhancement (ADE)?

Antibody-dependent enhancement (ADE) has not been identified as a concern related to SARS-CoV-2 infection or following COVID-19 vaccination. In fact, a body of evidence has suggested that ADE will not be a concern:

  • First, most people have been infected with other coronaviruses in their lifetime, and ADE has not been identified as a result of these infections.
  • Second, in human studies, people previously infected with coronavirus were infected with different types of coronavirus, and they did not experience enhanced disease.
  • Third, experimental animals vaccinated against SARS-CoV-2 did not develop enhanced disease when challenged, or infected, with the virus.
  • Fourth, when people with COVID-19 received plasma containing SARS-CoV-2 antibodies, they did not experience enhanced disease.
  • Finally, millions of people have been vaccinated against COVID-19, and some of them have subsequently been infected with SARS-CoV-2, or one of its variants, and none of them have shown evidence of ADE.

For these reasons, ADE is not a concern for SARS-CoV-2 infections or vaccination. Scientists will continue to monitor the SARS-CoV-2 variants; however, it would not be expected that ADE will become an issue with the rise of new variants, as it has not been with the many types of coronaviruses and the existing SARS-CoV-2 variants to date.

Watch a short video in which Dr. Paul Offit explains why COVID-19 vaccines are unlikely to cause ADE.

Last updated 9/9/21

Does the COVID-19 vaccine cause fertility issues?

Infertility has not been found to be an issue in women or men infected with COVID-19, so it would not be expected to be a concern for the vaccine.

Unfortunately, misinformation about fertility-related issues has been circulating online. These concerns take two forms:

  1. Compromised fertility in the vaccine recipient – Original concerns related to a placental protein, called syncytin-1. This protein is associated with the placenta during pregnancy. Online claims promoted a paper suggesting that a small number of similar amino acids in the spike protein and the placental protein would cause vaccine-induced antibodies to react against syncytin-1.  This false notion has been addressed by Full Fact. Recent concerns have expanded to include males, suggesting that the vaccines can decrease sperm count. While fever can cause a temporary decrease in sperm count, there is no biologically plausible reason to expect that the vaccines would cause any long-term effect on sperm count.
  2. Compromised fertility in individuals near someone who recently received COVID-19 vaccine – This misperception conflates two concepts: effects on fertility and viral shedding. As mentioned above, the vaccines do not affect fertility in the vaccinated person, so there would not be a reason to expect that they would affect someone else’s fertility. Second, it assumes that recently vaccinated individuals shed virus or spike protein. Neither of these occur. While these vaccines cause the body to generate spike protein, they do not cause production of whole virus particles, nor do parts of the vaccine migrate to the nasal cavity. As such, a recently vaccinated person does not shed any part of the virus and cannot, therefore, spread vaccine-related components to another person.

Watch this short video in which Dr. Paul Offit discusses COVID-19, the vaccines and infertility.

You can read more about fertility and COVID-19 vaccines in this Vaccine Update article.

Last updated 5/25/2021

Will I be able to get the coronavirus vaccine at the same time as other vaccines?

The CDC recently updated their recommendations to allow people to get COVID-19 vaccines along with other vaccines. This decision was made due to experience with more than one vaccine given close in time with COVID-19 vaccines during emergency situations and with more understanding of the effects of the COVID-19 vaccines, suggesting a low likelihood of interference. However, studies will continue to monitor responses during these situations to ensure that unexpected events do not occur. The CDC change also took into account the increased susceptibility of individuals who missed routinely recommended vaccines during the pandemic.

Watch this short video in which Dr. Hank Bernstein explains the benefits of receiving routine vaccines at the same time as the COVID-19 vaccine.

Last updated 5/13/2021

Is there any hope that a vaccine will help people with lingering after effects from coronavirus?

The lingering effects of COVID-19 are concerning, and we still have much to learn about them. A vaccine will help from the point of view that if it decreases infections, fewer people will experience illness and, therefore, fewer people will experience long-term effects. But, it is not likely that a vaccine will address these effects in someone who was already infected.

Last updated 12/15/2020

How much does the coronavirus vaccine cost?

Coronavirus vaccines are free; however, the Federal Trade Commission (FTC) has warned of scams in which people are charging for vaccines. Read more here.

Also, of note, while the vaccines are free, insurance companies may have to cover the cost of administering the vaccine. You should not, however, be charged any out-of-pocket fees when you go for your vaccine.

Last updated 4/23/2021

Does the COVID-19 vaccine contain blood products?

The COVID-19 mRNA and adenovirus vaccines do not contain any blood products, including red blood cells, white blood cells or platelets. 

Watch this short video in which Dr. Offit talks about the ingredients used in the COVID-19 mRNA vaccines.

Last updated 3/1/2021

How can I know about COVID-19 disease in my community or where I am traveling?

Several tools have been developed to help public health officials, governments, businesses, and individuals make informed decisions. These tools use county-level data to provide guidance. Two that may be particularly helpful include:

  • COVID-Lab: Mapping COVID-19 in your community — Developed by PolicyLab at Children’s Hospital of Philadelphia, this tool allows you to see COVID-19 test positivity in counties throughout the United States. The tool also offers projections for how levels of disease are expected to change in the next four weeks based on current social distancing practices, population density, testing capacity, and anticipated temperature and humidity.
  • COVID-19 event risk assessment planning tool — Developed by teams at Georgia Institute of Technology and Applied Bioinformatics Laboratory, this tool offers information about gatherings by county throughout the U.S., showing the percent chance that at least one person will be COVID-19 positive in gatherings of different sizes. The calculations are based on results of data from COVID-19 antibody blood tests.

Last updated 12/15/2020

We don't talk about "herd immunity" for protection against influenza or other common viral infections, so why is it discussed so much with COVID?

Herd immunity is a concept used in public health to describe a situation in which the more people in a community immune to a particular pathogen, the fewer people available for that pathogen to infect. As the infectious agent spreads through a community, it has more trouble finding susceptible people if most of those around them are immune. In this manner, we rely on herd immunity for viruses, such as measles, rubella, polio, and chickenpox, among others, even if we are not having conversations about it. Influenza is more difficult because the virus changes so much from one year to the next and as such, vaccination does not offer long-term protection.

Related to COVID-19, herd immunity has been discussed more frequently for a couple of reasons. First, because this is a completely new virus, no one had pre-existing immunity. People can become immune to SARS-Co-V2, the virus that causes COVID-19, in two ways — through disease or through vaccination. By monitoring how many people are immune relative to the entire population, public health officials can offer informed guidance related to easing restrictions meant to stem spread of the virus.

Herd immunity can only be induced by vaccination. Never in history has any virus infection been eliminated because of immunity induced by natural infection.

Last updated 3/1/2021

Was the genome of the virus subject to peer review or FDA/CDC oversight?

The viral genome is not a product; it represents scientific knowledge, so organizations like the FDA or CDC would not have “oversight” over the information. However, this question gets at the heart of how science is done. Scientists by their nature are skeptics, and the scientific process is designed to challenge rather than accept results. In this manner, several points offer reassurance that the genomic sequence was vetted for accuracy:

  • The scientists who reported the genome isolated samples from several patients to examine the genome. Said another way, their data were not based on a single person’s infection. They had to confirm for themselves and for the quality of their research that what they found was accurate. They could not assume that the same virus was causing infections without actually gathering evidence of such.
  • Once they completed their study, they had to share it with colleagues, who would critically review it and maybe even ask for more experiments or clarifications before they could publish a paper sharing their results with the world. Peer-review is critical to the scientific process, which is why you may have heard about data that were not yet peer-reviewed during the pandemic. For scientists, that means that the work has not yet been vetted.
  • Several other labs also isolated samples from patients and reproduced the process. Their papers were also peer reviewed before publication. Reproducibility is a second critical component of the scientific process. Even if the genomic information passed peer review and was published, if other labs did not find the same thing, the information would be called into question.

In this manner, the pillars of scientific integrity — peer review and reproducibility — can offer everyone reassurance that the genomic sequence was accurate— not to mention the fact that vaccines based on the information have been effective at preventing infection.

Last update: 3/31/2021

I heard that steps were skipped to make a vaccine more quickly. Is that true?

While COVID-19 vaccines have been developed more quickly than has ever been done in the past, it was imperative that speed did not decrease safety.

In this case, the timeline was shortened without sacrificing quality by:

  • Skipping phase I or combining phase I with phase II trials — Since phase I studies include a small number of people and evaluate whether the candidate vaccine causes an immune response and is safe, scientists could look at data from a group of people as phase II was progressing to make these evaluations.
  • Manufacturing “at risk” — While completing the large phase III clinical trials, manufacturers began producing the vaccine, so that if it was shown to be safe and effective, they would have large numbers of doses ready. The reason this is not typically the approach is because if the vaccine does not work, the manufacturer will have spent a significant amount of money to produce something that needs to be thrown away.
  • Support efforts — While waiting for a vaccine to be ready, many other aspects of vaccine delivery were prepared, including:
    • Developing plans for how to distribute the first, limited quantities available
    • Ensuring adequate supplies for distributing and administering vaccine, like vaccine vials, syringes and other equipment needed to vaccinate
    • Establishing mechanisms for distribution to large subsets of the population, especially in countries in which mechanisms may not currently be in place. For example, many countries do not have standard programs for vaccinating older adults. So, planning how to reach those people, without unintentionally exposing them to a crowd in which the virus may be spread, was something that could be planned during vaccine development.

Watch this video in which Dr. Paul Offit explains the COVID-19 vaccine trials.

Last updated 12/15/2020

Do COVID-19 vaccines contain a microchip?

COVID-19 vaccines do not contain microchips. This idea is based on a false narrative and misinformation campaign waged online. You can find out more about where this idea came from on

Last updated 12/15/2020

If my baby has had some of her vaccines, is she protected from COVID-19? We are anxious for her to meet family members.

A baby’s vaccines should not be anticipated to protect the baby from COVID-19. So, when trying to decide when it may be safe for family to meet the baby during COVID, parents should not rely on other vaccinations as a source of protection. While some have hypothesized that other vaccines may be protective, this protection would not be specific to COVID-19, and no studies have actually been completed to test this theory.

Last updated 12/15/2020

COVID-19 video resources

This section of the page will house video resources and interviews related to COVID-19.

Update on SARS-CoV-2 vaccines
Vaccine Education Center (VEC) Current Issues in Vaccines webinar, Dec. 9, 2020 (Please note that you will need to register to gain immediate access to the recording. If you are a healthcare professional seeking continuing education credits for viewing this event, please review the continuing education information on this page.)

Talking about Vaccines with Dr. Paul Offit: COVID-19
This VEC playlist features several short videos in which Dr. Offit addresses common questions about COVID-19.

Talking about Vaccines with Dr. Hank Bernstein: COVID-19
This playlist features a series of short videos in which Dr. Hank Bernstein answers common questions about COVID-19 vaccines.

My COVID-19 Vaccine Experience
These short videos share personal experiences and decision-making related to receipt of the COVID-19 vaccine.

Vaccinate Your Family’s COVID-19 Vaccine Updates: Zoom Series Featuring Top Officials from FDA and CDC, series hosted by Vaccinate Your Family

Last updated: June 14, 2021

Reviewed by Paul A. Offit, MD on August 10, 2021

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.