A Look at Each Vaccine: Diphtheria, Tetanus and Pertussis Vaccines

Diphtheria, tetanus and pertussis are prevented by a childhood vaccine, called DTaP, and a newer vaccine for adolescents and adults, called Tdap.

The diseases


What is diphtheria?

The dangers associated with diphtheria come from the toxin released by the bacterium, Corynebacterium diphtheriae. The toxin makes it difficult for children to breathe and swallow, but it also attacks the heart, kidneys and nerves.

Incidence of diphtheria

In the 1920s, diphtheria was a common cause of death in children and adolescents. At its peak, about 150,000 cases of diphtheria occurred in the United States every year. The diphtheria vaccine, first used in the United States in the early 1940s, has virtually eliminated the disease. Now we see fewer than two cases a year.

Countries in Eastern Europe, especially Russia, suffered severe outbreaks of diphtheria in the mid-1990s. The outbreaks coincided with a noticeable drop in immunization rates.


What is tetanus?

Tetanus is another disease caused by a toxin-releasing bacterium, Clostridium tetani. Unlike most vaccine-preventable diseases, tetanus is not a disease that you catch from someone else. The bacteria live in the soil and usually enter the body following punctures or wounds that are not kept clean or include damaged tissues such as from burns, frostbite, or gangrene. Items likely to be contaminated with the tetanus bacteria include nails or pieces of glass that were lying on the ground.  

Given the playful, adventurous, and oftentimes injury-prone nature of children, it's important to immunize them against tetanus. Hand washing and bathing do little once the bacteria actually get under the skin.

Once under the skin, the bacteria make a toxin that causes muscle spasms. If these spasms affect the throat and jaw (lockjaw), they can interfere with breathing, causing suffocation. The tetanus toxin can also damage the heart.

Because of its presence in the environment and the noninfectious nature of this disease, eradication will not be possible through vaccination. Further, people cannot be protected from this disease because everyone around them has had a vaccine; that is, there is no protection from herd immunity.

Two populations most affected by tetanus

In developed countries tetanus is typically thought of as infecting wounds in adults who have injured themselves; however, in the developing world many infants suffer from neonatal tetanus. Infections in newborns result from poor sanitation either during or after delivery. Each year almost 200,000 infants succumb to infections with tetanus.


What is pertussis?

Pertussis (also known as whooping cough) is one of the most contagious diseases around. Caused by a bacterium (Bordetella pertussis), whooping cough makes children cough uncontrollably. The cough is often so hard and so persistent that children can't catch their breath and make a "whooping" sound when they attempt to breathe in against a windpipe severely narrowed by mucus. The cough can be so violent that people with pertussis crack ribs, break blood vessels, or develop hernias. Pneumonia or seizures can also develop. Young infants can also experience bouts of apnea.

Pertussis is unusual in that most children catch the disease from adults and not from other children. Because pertussis is often misdiagnosed and underdiagnosed, people do not always realize how common it is. In fact, it is estimated that every year in the United States between 600,000 and 900,000 adults and adolescents get pertussis!

Read a personal story about pertussis»

Why is pertussis sometimes called the “100-day cough?”

Severe coughing spells that come with pertussis are the main reason this illness is sometimes called the “100-day cough.” Imagine having 15 severe coughing spells in a day — coughing spells that cause vomiting and prevent you from sleeping; coughing spells so severe that you get a nosebleed or crack your rib; coughing spells that last for months. This is pertussis.

Five things you should know about pertussis include:

  • Pertussis is highly contagious; in fact, eight of 10 non-immune people will be infected when exposed to someone with the disease.
  • Pertussis is commonly misdiagnosed and under-diagnosed.
  • You can get pertussis more than once, and protection from the vaccine fades over time.
  • Older children and adults commonly transmit pertussis to infants and young children.
  • Pertussis can be particularly severe, even deadly, in infants.

Misdiagnosis, under-diagnosis, and fading immunity

Experts are aware that the actual number of pertussis infections each year is much greater than the number diagnosed. That’s because of:

  • Misdiagnoses: Because pertussis bacteria are only detected at the beginning of the infection, the test may be negative by the time someone seeks medical care.
  • Under-diagnoses: Because many adults who are ill do not go to the doctor, they are never diagnosed with pertussis.
  • Fading immunity: Since there is a vaccine, people expect to be immune, but booster doses are needed to maintain immunity. Tdap is the vaccine recommended for booster doses in adolescents and adults.

Susceptible infants

Although a pertussis infection can interfere with day-to-day life, adults tend to recover. Unfortunately, infants and young children with narrow windpipes are not always as lucky. Coughing episodes caused by pertussis often turn babies blue as they struggle to breathe. Sadly, some of them do not survive.

Because the most negatively impacted age group is infants, who are too young to get a vaccine, public health officials have recommended two ways to protect them in the interim:

  •  “Borrowed” immunity — Because pregnant women have previously been exposed to pertussis, receipt of a single dose of Tdap vaccine between 27 and 36 weeks’ gestation boosts the level of pertussis antibodies in their blood. The result is that their babies receive a higher level of maternal antibodies against pertussis that can protect them if they are exposed to the bacteria before vaccination. Recently, public health officials have suggested that pregnant women get the Tdap vaccine as early during this window of 27 to 36 weeks as possible to maximize the quantity of antibodies the baby may have at the time of birth. 
  •  Limited exposure — Family members who will be with the new infant for extended periods of time are also recommended to get a single dose of Tdap vaccine if they have not already had one. This recommendation promotes a technique called cocooning. Cocooning is like wrapping your baby in a blanket of protection — when everyone around them has been protected with a recent dose of the pertussis vaccine, babies are less likely to come into contact with the bacteria and, therefore, less likely to become ill before they develop their own protection from DTaP vaccine.

The vaccines

DTaP, Tdap, and Td Vaccines

The DTaP and Tdap vaccines both protect against three bacterial infections: diphtheria, tetanus and pertussis, whereas the Td vaccine only protects against diphtheria and tetanus. In addition, the vaccines vary in terms of who should receive them and the quantities of vaccine proteins they contain:

  • DTaP: The DTaP vaccine is given to infants and young children in a series of five shots ─ at 2 months, 4 months, 6 months, 15 to 18 months, and again at 4 to 6 years of age.
  • Tdap: The Tdap vaccine is different from the DTaP vaccine because it contains lesser quantities of diphtheria and pertussis proteins. For this reason, Tdap is much less likely than DTaP to cause side effects such as pain, redness and tenderness in adolescents and adults. The Tdap vaccine is recommended for most people 11 years and older who have not previously received it:
    • Adults who are going to be around infants, including those who are 65 and older
    • Those 65 and older who have not had Tdap previously should get a dose in place of their next Td vaccine
    • Pregnant women should get one dose of Tdap vaccine between 27 and 36 weeks’ gestation during each pregnancy. Although anytime during this window is acceptable, the best time to get the vaccine is early during this window.
  • Td: The Td vaccine is the one people commonly think of when they think of getting their tetanus booster. Like Tdap, it contains lesser quantities of diphtheria protein to reduce the occurrence of side effects in adults. It was once recommended that adults get this vaccine every 10 years. Current recommendations for adults are to replace their next dose of Td with the Tdap vaccine if they have not already had it. 

Diphtheria vaccine

How is the diphtheria vaccine made?

The bacteria that causes diphtheria makes a harmful protein, called a toxin. People who develop an immune response to this toxin are protected against the disease. The diphtheria vaccine is made by taking the diphtheria toxin and inactivating it with a chemical. The inactivated toxin is called a "toxoid." Once injected, the toxoid causes an immune response to the toxin, but, unlike the toxin, doesn't cause disease.

What are the side effects of the diphtheria vaccine?

The diphtheria vaccine can cause mild side effects such as pain or soreness in the local area of the shot and occasionally a low-grade fever.

Tetanus vaccine

How is the tetanus vaccine made?

The bacteria that causes tetanus makes a harmful protein, called a toxin. The name of the tetanus toxin is tetanospasmin. People who develop an immune response to this toxin are protected against tetanus. The tetanus vaccine is made by taking the tetanus toxin and inactivating it with a chemical. The inactivated toxin is called a "toxoid." Once injected, the toxoid elicits an immune response against the toxin, but, unlike the toxin, doesn't cause disease.

What are the side effects of the tetanus vaccine?

Like the diphtheria vaccine, the tetanus vaccine can cause mild side effects such as pain or soreness in the local area of the shot and occasionally a low-grade fever.

The tetanus vaccine is also a rare cause of a severe allergic reaction. It is estimated that this allergic reaction could occur in about one of every 1 million children who receive the tetanus vaccine, and could include hives, difficulty breathing or a lower blood pressure. The allergic reaction can be treated with medications.

Pertussis vaccine

How is the pertussis vaccine made?

The bacteria that cause pertussis make several harmful proteins, called toxins. People who develop an immune response to some of these toxins are protected against disease. The pertussis vaccine is made by taking two to five of these toxins and inactivating them with a chemical. The inactivated toxins are called "toxoids." Once injected, the toxoids elicit an immune response against the toxins, but, unlike the toxins, don't cause disease.

The latest version of the pertussis vaccine was released in the fall of 1996. This vaccine is called the "acellular" pertussis vaccine (or aP) and is purer than the old "whole cell" pertussis vaccine. The "old" pertussis vaccine still contained a killed form of the whole pertussis bacteria. Because individual bacteria are sometimes called cells, the "old" pertussis vaccine was called the "whole-cell" vaccine. On the other hand, the new pertussis vaccine takes advantage of advances in protein chemistry and protein purification. Because the whole killed pertussis bacteria are no longer present, the "new" pertussis vaccine is called the "acellular" vaccine.

What are the side effects of the pertussis vaccine?

The "old" pertussis vaccine, called the "whole cell" vaccine, had a high rate of mild and severe side effects. Mild side effects such as pain and tenderness where the shot was given, fever, fretfulness and drowsiness occurred in as many as one-third to one-half of children who received the vaccine. Severe side effects, such as persistent, inconsolable crying occurred in one of every 100 doses, fever greater than 105 degrees occurred in one of every 330 doses, and seizures with fever occurred in one of every 1,750 doses.

The new "acellular" pertussis vaccine, the one that has been in use in the United States since 1996, has much lower rates of both mild and severe side effects. Mild side effects such as pain and tenderness at the injection site occur in about one-third of children, most often after the fourth or fifth dose. More severe reactions occur in about one of every 10,000 children. Severe reactions can include fever of 105 degrees or higher, fever-associated seizures, inconsolable crying, or hypotonic-hyporesponsive syndrome, a condition in which a child can become listless and lethargic with poor muscle tone for several hours. (see Are vaccines safe?).

Unfortunately, recent data suggests that the tradeoff for increased safety was decreased vaccine effectiveness. Children who received the “acellular” version of pertussis vaccine become susceptible more quickly than those who received the “whole-cell” version. However, it is unlikely that we would return to using the older version; instead, additional booster doses may be recommended until a newer version of the vaccine that is both safe and more effective can be developed.

Other questions you might have

Should babies who cry uncontrollably after DTaP vaccine receive additional doses?

Babies who experience uncontrollable crying after the DTaP vaccine are considered to have a “precaution” to getting future doses of the vaccine, meaning that they can still receive future doses of the DTaP vaccine; however, the relative risks and benefits should be discussed with the child’s doctor before the vaccination is given.

Because pertussis, in particular, is circulating in many parts of the country and young infants are most susceptible to complications from the disease, the relative benefits of the vaccine may still outweigh the risks. Previous experience has shown that in most cases, infants who experience inconsolable crying after the first dose of DTaP do not experience the same reaction after subsequent doses.

Should teenagers and adults get the pertussis vaccine?

Pertussis is common in teenagers and adults. Therefore, a vaccine to prevent pertussis in teenagers and adults is of great benefit. However, the old “whole cell” pertussis vaccine and the "acellular" pertussis vaccine for young children (part of the DTaP combination vaccine) had a high rate of side effects when given to people older than 7 years of age. A newer "acellular" pertussis-containing vaccine is available for older children and adults (part of the Tdap vaccine).

Because adolescents and adults can transmit this disease to infants who are too young to have received their series of the DTaP vaccine, it is imperative that adults around the baby are immune. The phenomenon in public health is called “cocooning” because the immunized adolescents and adults essentially provide a barrier around the baby to keep pertussis infections at bay. Parents, grandparents and childcare providers should all be immunized before the baby is born. (Also see vaccines during pregnancy.)

How can I protect my newborn from pertussis?

Pertussis can be a dangerous disease for a new baby. Because of their small airways and the amount of mucus caused by infection with pertussis, babies have trouble breathing, often turning blue during their coughing spells. Every year in the U.S. about 20 to 25 children die from pertussis, most are young babies who have not been fully immunized.

There are several things that you can do to help protect your baby from pertussis. Babies get a vaccine to protect them from pertussis when they are 2 months, 4 months, and 6 months of age. They get an additional dose at 15 to 18 months. However, babies are most susceptible during their first few months of life either because they have not gotten the vaccine yet or because the dose they received did not fully protect them. During this time, you can protect your baby by making sure that all of the adults (or siblings) who will be around the baby are protected - this is what public health personnel call the "cocooning" method.

There is a vaccine available for adolescents and adults called Tdap. The "p" means that it contains a pertussis component. Pregnant women should receive the Tdap vaccine between 27 and 36 weeks’ gestation during each pregnancy. Although any time during this window is acceptable, public health officials recommend getting the vaccine as early as possible during this window. If you are past 36 weeks in your pregnancy, be sure to ask for the Tdap vaccine before being discharged from the hospital. Your spouse, the baby's grandparents and any other adults who will commonly be around the baby should also get the vaccine in advance of your delivery.

Additionally, you can encourage hand washing before people touch the baby, and if anyone has a cough, try to limit the baby's exposure to this person. Unfortunately, people are not only contagious in the first few weeks of the severe coughing stage, but also in the one- to two-week period leading up to cough onset. During this period, symptoms may resemble cold-like respiratory symptoms (e.g., runny nose, sneezing, occasional cough).

If I had whooping cough as a child, do I still need to get the vaccine before being around an infant?

Protection after a pertussis infection is not life-long. Because infants are at increased risk of suffering complications and death from pertussis infections, adults and teens who will be around them, including childcare providers, should have a single dose of the Tdap vaccine.

If I had the DTP vaccine as a child, do I need the booster vaccine for pertussis?

Yes. Adults who have not previously gotten the Tdap vaccine should receive a single dose. Some people are recommended to get the vaccine as soon as possible, including healthcare workers and people who will be in contact with infants. Pregnant women should get the Tdap vaccine between 27 and 36 weeks’ gestation during each pregnancy because pertussis can be fatal to young infants. Although any time during this window is fine, public health personnel suggest earlier rather than later during the window for maximum protection for the baby.

Read about a mom who lost her 3-week-old baby when they both got pertussis»

The Tdap vaccine is also recommended for all adolescents 11 or 12 years old.

Can people over 65 get the Tdap vaccine?

Although the vaccine was originally recommended only for adults less than 65 years old, the recommendation was changed in Oct. 2010 due to ongoing pertussis outbreaks primarily in California, but in other locations throughout the United States as well.

The original recommendation excluded people 65 and older because the studies were done in people less than 65 years old. However, the theoretical risks associated with vaccines not being extensively tested in this age group are now outweighed by the real risks of spreading pertussis, particularly to infants too young to be immunized.

Relative risks and benefits

Do the benefits of the diphtheria vaccine outweigh its risks?

Diphtheria is an extremely rare cause of disease in the United States. Over the past 20 years there have been only about 25 cases of diphtheria causing five deaths. The last death from diphtheria in the United States was in 2003. Most cases of diphtheria are imported; in fact, there have been no cases in U.S. residents since 1999. On the other hand, the diphtheria vaccine has no serious side effects. So although the risk of disease and death from diphtheria is very small, the risk of severe adverse reactions or death from the diphtheria vaccine is zero. In addition, drops in immunization rates in Eastern Europe and Russia taught us how quickly outbreaks of diphtheria can return. For these reasons, the benefits of the diphtheria vaccine outweigh its risks.

Do the benefits of the tetanus vaccine outweigh its risks?

Although tetanus bacteria are everywhere, tetanus is an uncommon cause of disease in the United States. But it’s probably not as rare as you may think. Between 2006 and 2011, an average of 24 cases of tetanus was reported each year in the United States with four or five deaths. On the other hand, although the tetanus vaccine can be a very rare cause of a short-lived allergic reaction called "anaphylaxis," the tetanus vaccine does not cause death. Therefore, the benefits of the tetanus vaccine outweigh its risks. In addition, because most of the disease and death from tetanus occur in the elderly, it is important to get booster immunizations every 10 years.

Do the benefits of the pertussis vaccine outweigh its risks?

This question is best answered by taking a look at the side effects of the old pertussis vaccine. The old pertussis vaccine had a high rate of severe side effects such as persistent inconsolable crying, fever higher than 105 degrees, and seizures with fever. Due to negative publicity surrounding this vaccine, the use of the pertussis vaccine decreased in many areas of the world. For example, in Japan, children stopped receiving the pertussis vaccine by 1975. In the three years before the vaccine was discontinued, there were 400 cases and 10 deaths from pertussis. In the three years after the pertussis vaccine was discontinued, there were 13,000 cases and 113 deaths from pertussis. It should be noted that although the side effects of the old pertussis vaccine were high, no child ever died from pertussis vaccine.

The Japanese Ministry of Health, realizing how costly its error had been, soon reinstituted the use of pertussis vaccine. The children of Japan proved that the benefits of the old pertussis vaccine clearly outweighed the risks. The new "acellular" pertussis vaccine has a much lower risk of severe side effects than the old "whole cell" vaccine.

Pertussis is quite common in the United States. More than 41,000 cases of pertussis and 18 deaths were reported to the CDC during 2012. However because of under diagnosis and misdiagnosis, this number is likely to be a vast underestimate of the number of cases that actually occurred. It is estimated that most years between 600,000 to 900,000 cases occur in adolescents and adults. Sadly, most of the deaths from pertussis occur in young infants who struggle to breathe against a narrowed windpipe, leading them to turn blue or suffer spells of apnea. Because the pertussis vaccine does not cause death, the benefits of the pertussis vaccine clearly outweigh its risks.

Diseases risks


  • Damage to heart, kidneys and nerves
  • Can be fatal


  • Severe muscle spasms
  • If muscles in throat and neck spasm, it may lead to suffocation and death
  • Heart damage


  • Uncontrollable coughing for weeks or months
  • Severe coughing attacks can crack ribs, break blood vessels, or cause hernias.
  • Pneumonia or seizures
  • Bouts of apnea (young infants)
  • Can be fatal

Vaccine risks

  • Pain, redness and swelling at the injection site
  • Mild fever
  • Fussiness, fatigue, lack of appetite
  • Nausea, vomiting, diarrhea, stomach ache
  • Extensive swelling of the limb where the shot was given (about 3 in 100 people)
  • Severe reactions (about 1 in 10,000 people):
    • Fever of 105 degrees or higher
    • Fever-associated seizures
    • Inconsolable crying
    • Hypotonic-hyporesponsive syndrome, a condition in which a child can become listless and lethargic with poor muscle tone for several hours


  • Plotkin SA, Orenstein W, and Offit PA. Diphtheria Toxoid in Vaccines, 6th Edition. 2012, 153-166.
  • Plotkin SA, Orenstein W, and Offit PA. Tetanus Toxoid in Vaccines, 6th Edition. 2012, 746-772.
  • Plotkin SA, Orenstein W, and Offit PA. Pertussis Vaccines in Vaccines, 6th Edition. 2012, 447-492.

Reviewed by Paul A. Offit, MD on November 16, 2016

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.