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Vaccine Science

Vaccines: Are They Natural?

Many of today’s consumers crave organic, all-natural, or free-range products. Willing to pay more and drive further to get these products, they believe they are keeping their families healthy. Some of these same people forego vaccines claiming that they are not natural.

So, what is natural?

According to the Merriam-Webster dictionary, natural means “being in accordance with or determined by nature.” Viruses and bacteria are natural; diseases caused by them are natural.

Because vaccines are made using parts of the viruses and bacteria that cause disease, the ingredient that is the active component of the vaccine that induces immunity is natural. However, critics point to other ingredients in vaccines or the route of administration as being unnatural.

Vaccine Ingredients

“Green our vaccines” is a common mantra of those who believe that the ingredients in vaccines are harmful—and unnatural. However, vaccine vials contain well-characterized ingredients in known quantities.

Vaccines contain three types of ingredients other than the virus or bacterium of interest:

Some wonder about the amount of different additives in vaccines or the cumulative effect from several vaccines. This is a valid concern; in fact, the Swiss chemist Paracelsus coined the phrase, “the dose makes the poison.” However, the good news is that the quantities of ingredients in vaccines are determined to be the lowest amounts necessary and when vaccines are given together, they must be studied together. So the quantities of ingredients in vaccines have been determined to be safe.

Route of Administration

Viruses and bacteria typically enter the body through our noses or mouths. With the exceptions of the oral rotavirus and intranasal influenza vaccines, most vaccines are given as a shot. While at first glance the injections appear to be different or “unnatural,” they are not when you consider what happens in each case.

When viruses or bacteria enter the body through the nose or mouth, they are detected by cells of the immune system which line the surfaces of these areas of entry. These “foreign invaders” are ingested by immune cells and processed in lymph nodes in the region of the infection. The immune response has two aspects, local and systemic. The immune cells are produced near the site of the infection, but they are dispersed throughout the body via the bloodstream. After the infection has been resolved, a small number of immune memory cells continue circulating to monitor for future infections. Because these memory responses are specific, subsequent exposures to the same virus or bacterium generate a quicker and stronger immune response that completely prevents or significantly lessens the effects and duration of illness.

Vaccines are no different. Although common belief is that vaccines are injected directly into the bloodstream, they are actually administered into muscle or the layer of skin below the dermis where immune cells are produced and circulate as occurs following natural infection.

In Conclusion

The active ingredients in vaccines are the parts of the viruses or bacteria to which we make an immune response. The additional ingredients are determined to be the lowest plausible quantities and are studied as part of the vaccine during safety testing. The immune system responds in the same way it would to the virus or bacteria following unexpected introduction. So while not natural in that they are given at specified times, vaccines offer a controlled way to protect ourselves from the viruses or bacteria that cause illness.

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How vaccines work

A person who has been ill with a disease is less likely to get the disease again than someone who never had it. This is because when a person is sick, the body makes infection-fighting antibodies. After the person recovers, these antibodies move around in the person's body and watch for that disease to reappear. If the antibodies detect disease, they quickly signal the body to start making more antibodies to fight the infection. This person is considered to be immune from the disease and may not even know that he or she was exposed to it again.

A vaccine works like the first encounter with disease in that it allows the body to make antibodies that will circulate and watch for the disease to come again. The difference between a vaccine and the first encounter with a disease is that the vaccine causes immunity without causing illness.

Learn more about how vaccines work»

View a video clip about how someone becomes immune to a disease, by selecting "What is immunity?" in the "Vaccines and Your Baby" video»

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How vaccines are made

It takes several years to make a vaccine and test it for its safety and utility. There are currently a handful of different approaches used to make vaccines:

To learn more about how some of these vaccines are made, view the "Vaccines and Your Baby" video, and go to the "Click here to learn about specific vaccines" section.

Learn more about how vaccines are made»

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Which vaccines are made using cell lines from prematurely terminated pregnancies?

The vaccines made using cell lines originally isolated from two elective abortions performed in the early 1960s include:

The cell lines are maintained in laboratories so that no further abortions need to be performed to make these vaccines. The reasons that fetal cells were originally used included:

So, as scientists studied these viruses in the lab, they found that the best cells to use were the fetal cells mentioned above. When it was time to make a vaccine, they continued growing the viruses in the cells that worked best during these earlier studies. 

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What Does It Take to Make a Vaccine?

People critical of vaccines often cite issues related to how a vaccine is made, such as the amount of time a vaccine has been tested, the number of people who received it, and the ingredients in the vaccines. An understanding of how vaccines are made may rest some of these concerns.

Initial ideas

Usually a vaccine begins not at a pharmaceutical company, but in a research laboratory in a university, medical center or small biotech company. Scientists in these laboratories are most often funded by grants from the government or private foundations. These scientists often spend years researching whether their ideas work, developing reagents and tests to measure their success (or lack thereof), and finally, using animals to test their ideas. In some cases the ideas are tested in small animals like mice, rats or rabbits and then again in larger animals such as monkeys. 

During this time, several different scientists or groups of scientists may be working toward the same goals, e.g., developing a vaccine against a certain virus or bacteria. The progress of these scientists is evaluated by other scientists through presentations at scientific meetings and peer-reviewed papers in journals. Scientists working at pharmaceutical companies often attend these meetings and review journals to see what ideas seem to be working. If any of the work seems promising, the pharmaceutical scientists may approach those working on it about expanding their research toward product development. This process may take 5 to 10 years. 

The great majority of university scientists never develop ideas that are turned into products; most enjoy the success of adding to the general body of knowledge that is science.

Phase I trials

Once an idea appears promising, it must be tested in a small number of healthy adults. These studies usually include less than one hundred people and answer two main questions: does the vaccine generate the expected immune response and is the vaccine safe? 

During phase I trials, scientists at the pharmaceutical company must study how to make the vaccine in a quantity large enough for preliminary trials. They also must determine what preservatives or stabilizers to add so that the vaccine does not break down and whether any adjuvants are necessary to generate a strong enough immune response. Any preservatives, stabilizers or adjuvants that are going to be in the final vaccine must be used in the trials.

In addition, company personnel must develop assays that consistently show positive results when expected and negative results when expected, and they must complete an application to inform the Food and Drug Administration (FDA) of their intentions. 

This phase often takes one to two years to complete.

Phase II trials

The next phase of trials involves several hundred people. During this phase, scientists try to determine the proper dose of vaccine to be given, and they continue to study the vaccine's safety. They also continue to define methods for manufacturing the vaccine, stabilizing the product, determining packaging vials, and establishing assays necessary for the trials. An important aspect of this phase is to establish manufacturing consistency, so that each lot comes out with similar results. 

The manufacture of the vaccine must also be completed in the building that would be used to make the final product. The company must continue to keep the FDA apprised of its progress and results during this time; at any time during this process the company or the FDA can decide against continued development.

While phase II can take as little as two years, it often takes much longer to complete all of the work necessary for this phase of development.

Phase III trials

This is the final stage of development before a company requests product licensing, and it takes three to four years to complete.

Studies in this phase of development include thousands of study participants who are similar to the population that will receive the vaccine (e.g., infants for a new infant product). The number of participants is calculated so that statistical differences between the experimental group and control group can be observed. These calculations depend on frequency of disease in the population, estimated participant dropout rates, and ability of the assays being used to show differences. For example, trials on the rotavirus vaccine (RotaTeq® and Rotarix®) required about 130,000 participants because the companies had to determine that these two vaccines did not cause a bowel obstruction caused by an older version of the vaccine (Rotashield®). 

During this phase, the company must also continue working on final facility and assay specifications and study how long the vaccine can be used before it expires, taking into account how it will get to the users (doctors' offices, for example) and how it will be stored. Any testing sites (those recruiting patients or testing samples) must be monitored to ensure that protocols are being followed consistently. Samples must be collected and analyzed to study the participants' immune responses, whether they get the disease, and whether they suffer adverse reactions.

During these studies, as with the previous phases, no one working with the patients, testing the samples collected from patients, or calculating the results, knows which participants received the vaccine and which did not. 

After completion of these studies, it takes another year and a half to two years for the company to review the data, complete the product license request, and launch the product. The FDA, which does site visits throughout the entire process, then takes about 10 months to further study the data before the product can be offered to the public.

After licensure, experts for the Centers for Disease Control and Prevention (CDC) will also review the data and determine who should be able to get the vaccine. This is essentially the third set of scientists reviewing the same data. Often, the company or healthcare providers who helped run the phase III studies will also publish the results in a scientific journal for review by other scientists.

By the time the product is offered to the public, it has been studied for at least 10 to 15 years (usually longer) in tens of thousands of study participants, by thousands of scientists, statisticians, healthcare providers and other personnel, and has cost about $800 million dollars to produce. There are many products that never reach this stage. Companies are constantly evaluating a product during the trials to determine whether they are worth pursuing. Many ideas are abandoned during the different trial phases.

After licensure

Because rare side effects may be observed once the vaccine is given to the larger population, the vaccine continues to be studied. In addition to monitoring by the manufacturer, there are two systems of long-term monitoring, the Vaccine Adverse Events Reporting System (VAERS) and the Vaccine Safety Datalink (VSD).

VAERS gathers reports of adverse events. Anyone can report these events; however, because this reporting system is voluntary, it cannot be used to prove there is a problem. 

If the reports suggest a potential problem, scientists can examine the Vaccine Safety Datalink, a system that can mine data from a group of eight large managed care organizations, to determine if a group of vaccine recipients has experienced a greater occurrence of the adverse event than a similar group who has not received the vaccine. Scientists can also set up a hypothesis-driven research study to examine whether the vaccine is causing the adverse event. These types of studies have been able to detect adverse events as rare as 1 in 100,000.

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Vaccination or Immunization?

Although we commonly use the words vaccination and immunization interchangeably, they are not exactly the same.

Vaccination was first coined as a term when Edward Jenner used cowpox to immunize people against smallpox. The word vaccination comes from the Latin word vaccinae meaning “of the cow.”

Immunization means immunity induced by a biological agent. The word immunization comes from the Latin word Immunes, referring to “a group of soldiers who once having fought and survived a battle never had to fight again.” In our society immunity has come to mean freedom from anything burdensome; in the case of vaccines, our children are the soldiers, the vaccines are the battle and the freedom gained is from disease.

There are two forms of immunization. Active immunization means administering a vaccine, so that the recipient generates her own immune response. Passive immunization means administering antibodies or antitoxins from another source to protect the recipient. Antibodies passed from mother to child through breast milk are an example of passive immunization.

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Number of vaccines then and now

Q. I recently heard that in the past children were exposed to more in vaccines than they are today. How can this be now that we have so many more vaccines?

A. Science has improved through time, so today’s vaccines only contain those proteins necessary to protect someone from the disease in question. The most dramatic change in this regard was the pertussis vaccine. The first version, called the whole-cell pertussis vaccine, contained about 3,000 proteins whereas the version used today, known as the acellular pertussis vaccine, only contains 2-5 proteins. Learn more»

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Vaccines and susceptibility to disease

A recent study of data from more than 13,000 medical records of young children in Germany showed that when children who received vaccines were compared with those who had not, the vaccinated children were:

Both vaccinated and unvaccinated children had a decreased risk of disease as they got older which makes sense as they would likely be immune to more infections, having developed protection at younger ages. 

Read the full article»

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Specific versus nonspecific immunity

The immune system is composed of two parts: innate and adaptive.

The innate immune system is the fast-acting first line of defense and affords nonspecific immunity through both physical and chemical means. Examples of physical components of innate immunity include our skin and nasal hairs. Chemical components include things like acids in the stomach, enzymes in sweat and saliva, and inflammatory responses that cause heat, redness, swelling and pain locally.

The adaptive immune system takes longer to activate, but responds specifically to an invading pathogen. Antibodies generated by B cells are examples of the adaptive immune response. Immunological memory, in which our bodies remember previous pathogens and activate more rapidly, is also an example of adaptive immunity. Vaccines employ the adaptive immune system to protect us from future encounters with viruses and bacteria.

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Vaccines and antibiotics

Vaccines and antibiotics are two of the most powerful tools against bacterial infections. Vaccines work by preventing infections whereas antibiotics work by treating them. Antibiotics were first discovered in the early 1900's when a drug called sulfanilamide was found to protect people from fatal bacterial infections such as pneumococcus. Pneumococcus causes pneumonia, bloodstream infections, and meningitis.

Perhaps the most well known antibiotic is penicillin. By the 1940s penicillin could be produced in large quantities and was recognized as an easy way to save people from disease and death caused by pneumococcus. Doctors believed that they could eliminate pneumococcus with these new tools; thus interest in learning more about preventing pneumococcus by vaccine waned.

Dr. Robert Austrian was a physician who continued studying pneumococcal infections, first in New York and later throughout the country. His studies showed that while people treated with penicillin were less likely to die from their infections, pneumococcus was still infecting as many people as it did before penicillin was available. He also found that people who got the most severe infections with pneumococcus died regardless of whether or not they were treated with antibiotics.The only way to protect them would be to prevent their infections in the first place; that is, to immunize them.

While Dr. Austrian was completing his studies, people were continuing to be infected and treated for pneumococcal infections using antibiotics, such as penicillin. Antibiotics resolve infections by stopping the bacteria from reproducing themselves.

However, bacteria respond in a "survival of the fittest" manner. These antibiotic-resistant bacteria continue to reproduce and can be passed on to others.

Antibiotic resistance was discovered shortly after penicillin came into popular use. By 1967, pneumococcal strains resistant to penicillin began to appear. At first, the answer to antibiotic resistance was simple. If the bacteria resisted penicillin, use another antibiotic. However, by the 1980s and 1990s, as pneumococcus and other bacteria became more resistant to antibiotics, doctors were running out of options. Indeed, today there are strains of bacteria for which no existing antibiotic will work. Although scientists continue to research, design and test new antibiotics, the process is slow and expensive.

In the case of pneumococcus, we have had some reprieve—Dr. Austrian's first vaccine became available in the late 1970s and a second version, still used for adults today, was introduced in 1983. Although Dr. Austrian's vaccine worked in adults, it did not work well in young children. In 2000, another version that works better in children also became available. As more people in the community are immunized against a particular type of bacteria, such as pneumococcus, there are fewer opportunities for the bacteria to reproduce and infect others. Thus, vaccines have become one of our most important tools in the fight against antibiotic resistance.

To stem resistance, in addition to getting vaccines, people should:

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Vaccines and aluminum

Q. I have heard that aluminum in vaccines is safe because we are exposed to it in the environment. I am not comfortable with this explanation because with vaccines the aluminum is injected. Isn’t that more dangerous?

A. Regardless of how aluminum enters the body, it is treated the same way once it gets into the bloodstream. A protein in the blood, known as transferrin, binds the aluminum and transports it to the kidneys where it is eliminated. About half of the aluminum is eliminated within 24 hours. Aluminum becomes a problem when someone’s kidneys are not functioning properly or at all AND when large quantities of aluminum are administered, such as in antacids. The quantities of aluminum in vaccines are so minute that they do not cause a detectable change to aluminum levels in the blood.

Read more: 

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DNA in vaccines

Q. Do you have any information about the danger of DNA in vaccines?

A. The vaccines made using human embryo cells include those for chickenpox, rubella, hepatitis A, and one version of the rabies vaccine. The amount of human DNA remaining in the vaccine preparation is minimal (trillionths of a gram) and highly fragmented; therefore, it is not harmful.

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Vaccines and Egg Allergies

Editor’s Note: This article was written by Jonathan Spergel, MD, PhD. Dr. Spergel is Chief of the Allergy Section and Co-Director of the Center for Pediatric Eosinophilic Disorders at The Children’s Hospital of Philadelphia.

Egg allergy

Egg allergy is one of the more common pediatric food allergies. It typically affects just 0.5 percent of the pediatric population (less than 1 of every 100 children) and 5 of every 100 children with allergies. Reactions to egg can vary from life-threatening anaphylaxis to atopic dermatitis (eczema) to hives.

Food allergies are diagnosed by physical examination, previous experience, and allergy testing. There are two types of allergy testing: skin testing and blood testing for specific antibodies to eggs (commonly called RAST testing). Each test has advantages and disadvantages. In general, if you are negative on either test, you do not have an allergy to egg; however, the blood test can be negative in about 5 of every 100 children who actually have an egg allergy. A positive blood or skin test indicates a potential to react to egg, and the larger the skin or blood test, the more likely it is that a reaction will occur. However, the size of the skin or blood test does not correlate with how severe a reaction will be.

Egg allergies and vaccines

Because influenza and yellow fever vaccines are both made in eggs, egg proteins (primarily ovalbumin) are present in the final products.

In the case of the yellow fever vaccine, quantities are sufficient to cause allergic reactions in susceptible patients. If you or your child is allergic to eggs and you are interested in getting the yellow fever vaccine, you should make an appointment with an allergist.

Advances in technology have allowed the quantities in current influenza vaccines given as shots to be so minimal that people with egg allergies can now receive the influenza shot. However, because very low quantities of egg protein are still present, people with this allergy should remain in the provider’s office for about 30 minutes after receiving the vaccine.

What about future doses of the vaccine?

Current protocols require that people with egg allergies repeat the process with an allergist each time they get the vaccine because the protocols do not prevent the allergy, they simply provide a way to get around the allergic response in the short term, so that the vaccine can be given safely.

References

Erlewyn-Lajeunesse et al, BMJ 2009
Piquer- GIbert M, Allergol Immunopathol (Madr). 2007 Sep-Oct;35(5):209-12
James et al, J Pediatr. 1998 Nov;133(5):624-8
Saltzman, et al. J Aller Clinical Immuno 2009; 123 (2):S175

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Animals and vaccines

The benefits of vaccines are often discussed as they relate to people. Vaccines keep people healthy, decrease the transmission of diseases throughout the population, and decrease the costs associated with medical care. However, animal vaccines are of benefit to people as well. Obvious benefits include keeping pets healthier and decreasing the costs of veterinary care. But they also decrease the number of human cases of disease by preventing diseases that are transmitted to humans by animals (e.g., rabies). And by keeping farm animals, such as chickens, healthy with immunizations, we can raise more animals and our grocery bills stay lower.

Animal vaccines can prevent human disease

One of the best methods for controlling human rabies in the United States is by immunizing pets. In some other countries where dogs and cats are not routinely immunized against rabies, the animals are the major source of rabies cases in humans. However in the U.S., most exposures occur by inadvertent contact with wildlife. The types of wildlife that account for mostexposures in the U.S. vary, depending upon the geographic location. In the eastern part of the country, raccoons account for most human exposures and in the western and central parts of the U.S., skunks are the primary transmitters to humans. Foxes account for most human cases in the northeastern states that border Canada and in Alaska.

Animal vaccines can help the grocery bill

During the 1928 presidential campaign, Republicans promised that a vote for Herbert Hoover would continue the prosperity started by Harding and Coolidge; they promised the proverbial "chicken in every pot." But it wasn't a president who delivered on this promise, it was a scientist. Dr. Maurice Hilleman developed a vaccine that would ultimately decrease the cost of chicken from two dollars to 40 cents and eggs from 50 cents to 5 cents per dozen. The vaccine that Dr. Hilleman developed prevents a disease in chickens called Marek's disease, which causes leg paralysis and cancers of the skin, ovaries, liver, kidneys, heart and spleen of the animals. It is caused by a herpesvirus that spreads easily throughout a flock as well as to neighboring flocks. Prior to the availability of the vaccine, Marek's disease claimed about 20% of the chicken population throughout the country.

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E. Coli outbreaks and food contamination

In December 2006, 71 people in 5 states were sickened by lettuce contaminated with E. coli after eating at Taco Bell restaurants in the northeastern region of the U.S. The type of E. coli that caused this outbreak is one of the leading causes of food contamination. Each year approximately 110,000 illnesses and up to 80 deaths in the U.S. result from E. coli infection.

The bacterium typically lives in the intestine of cattle, so a primary source of contamination is undercooked beef. Another common source is leafy vegetables that are not washed well enough or were exposed to raw beef products. Exposure to very small quantities of this bacteria are sufficient to cause illness. Similarly, the illness can be passed on to others without good hand hygiene after using the restroom or changing diapers.

The Taco Bell lettuce outbreak was in the media daily during the outbreak period. During this time, there were probably an additional 5 to 10 times as many cases of E. coli infection throughout the U.S.

Although we only hear about sporadic outbreaks, there are, in fact, E. coli infections that occur every day in the U.S. They are primarily caused by contaminated food or water, but because they affect individuals or a small group, they often go unreported, giving us a false sense that we are safe from these infections.

People sickened by E. coli typically have bloody diarrhea and abdominal cramping with no fever or a low-grade fever. About 8 of every 100 people will also develop a complication that damages the kidneys and could cause blindness or paralysis. Children under 5 years of age and the elderly are particularly susceptible to these complications. About 3 to 5 of every 100 people who suffer complications from E. coli infection will die from them.

Researchers are working to develop a vaccine that will effectively protect against this infection; however, there is still much to be done before a vaccine would become available.

Things that you can do to protect yourself in the absence of a vaccine include: eat only ground beef that has been completely cooked; keep raw meat away from other foods, particularly those that will be eaten raw; drink only pasteurized milk and juices; wash fruits and vegetables thoroughly even those that are labeled as pre-washed; drink tap or bottled water or water that you know has been chemically treated; and avoid swallowing water while swimming.

Finally, wash your hands with soap and water often, particularly after handling uncooked meats, fruits, or vegetables, and after using the restroom.

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Updated: January 2012

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