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Vaccine Safety

"One size fits all vaccines"
Questions related to vaccine safety

"One size fits all vaccines"

Recent discussions with parents concerned about the safety of vaccines have made mention of "one size fits all vaccines." Specifically, the concern is that the same vaccines are given to infants regardless of size, age or immunologic status. The following will address these concerns.

Infants versus adults

A popular misperception is that all vaccines are given at the same dose to infants and adults. However, there are specific adult and pediatric versions of hepatitis A, hepatitis B, and tetanus, diphtheria, and pertussis vaccines. In the cases of hepatitis A and hepatitis B vaccines, adults receive greater quantities of the components that afford protection in order to produce a protective response. However, in the case of the latter vaccines, the quantities of both diphtheria and pertussis are less than those found in pediatric doses because adults are more likely to experience side effects from these vaccines.

Vaccines and drugs are not created equal

Often, people are concerned about the dosing of vaccines because they compare them to drugs, which are given in different doses based on body weight. This is like comparing apples and oranges. Specifically, drugs work when a certain level is present in the bloodstream; therefore, the weight of a person is important. It takes more of a drug to see the same effect in a larger person than it does in a smaller person. This is similar to the effects of alcohol on a large man and a small woman.

Vaccines, however, do not function in the same way. For a vaccine to be effective, the cells of the immune system are important. Immune cells, called T cells and B cells, must be able to recognize the component of the vaccine, so that if a person comes into contact with that virus or bacteria again, these educated cells can become active and protect the person from an infection. Since these cells are throughout the body, they are usually educated near where the vaccine is given and then the cells, not the vaccines, travel throughout the body. Because of the way that vaccines work, they typically require very low quantities of active ingredients.

Vaccine doses

Vaccine doses are not chosen arbitrarily. During the four phases of vaccine development, different doses are tested to determine the lowest effective dose for the target age group. For example, the rotavirus vaccine was tested at quantities as low as one-tenth the current dose and up to 10 times the current dose.

Vaccine developers must practice good medicine and good economics. Giving larger doses of active ingredients than required would increase the side effects from and the costs of vaccines.

Learn more about vaccine development»

Individuals and public policy

Another common belief is that individuals are not considered when public policies are made. However, there are numerous special circumstances when people should or should not receive a particular vaccine based on their medical history. This is why people are typically advised to get vaccines in their doctor's offices where their medical records can be reviewed prior to the administration of any vaccines.

Some patients require vaccines not necessarily recommended for their age group because they are at an increased risk of getting a disease. For example, doctors caring for cancer and transplant patients follow special immunization recommendations because the patients' immune systems will be weakened as a result of their treatments. Similarly, children without a spleen or with an immune disorder called complement deficiency are suggested to get the meningococcal vaccine earlier than children without these conditions.

There are also circumstances when patients are not recommended to get vaccines based on their medical conditions. For example, adults with weakened immunity resulting from radiation or certain medications should not receive vaccines containing live viruses, such as measles, mumps, rubella, chickenpox, or shingles. Likewise, children or adults with egg allergies typically should not receive the influenza or yellow fever vaccines, and children with severe gelatin allergies may need to forego certain immunizations.

All 50 states allow individuals to forego immunizations that are not safe for them based on their medical histories.


Questions related to vaccine safety

Side effects and the body’s reaction to vaccines

Q. Is it true that side effects indicate that a baby’s body is reacting poorly to vaccines?

A. It is true that side effects are a reaction to a vaccine; however, they do not indicate that the immune system is reacting “poorly.” Quite the opposite, systemic side effects like fever indicate that the immune system is making an immune response to the vaccine. While it is reasonable to think that a fever is bad for a child, it actually helps the immune system work more efficiently. The problem with fevers occurs when they rise too quickly, sometimes leading to febrile seizures which, although frightening to see, are benign. In the case of fevers that result from vaccination, they tend to be what are considered “low-grade” fevers, so the concerns related to fevers from natural infections do not apply. The local side effects, such as pain, redness or swelling near the injection site, are responses to the physical disruption of muscles near the injection or the local immune response when white blood cells penetrate the area to respond to the “invader.”

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.

Learn more 

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.


Updated: February 2013

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