Are vaccines safe?

The American Academy of Pediatrics answers tough questions about childhood immunizations


There’s a lot of information available on vaccines, not all of it reliable. Here, pediatricians set the record straight:

I’ve heard that vaccines are not needed because the diseases were disappearing even before the vaccines were developed.
This is not true. Many diseases do not occur or spread as much as they used to, thanks to better nutrition, less crowded living conditions, antibiotics, and, most importantly, vaccines. However, this does not mean that the bacteria and viruses that are responsible for these diseases have disappeared. Immunizations are still needed to protect children from these diseases. For example, Haemophilus influenzae type b (Hib) diseases were a major problem a few years ago until the vaccine was developed for infants. Over several years, we went from 20,000 cases of Hib diseases to fewer than a few hundred. The vaccine is the only explanation for this decrease. Unvaccinated children are still at risk for Hib meningitis and other serious illnesses.



Most diseases have been virtually eliminated from the United States, so my child doesn’t need to be vaccinated, right?
Immunizations have reduced most diseases to very low levels in the United States. However, some of these diseases are still common in other parts of the world. Travelers can bring these diseases into this country. Without immunizations, these infections could quickly spread here. Immunizations also help people who cannot be vaccinated or who do not respond to vaccines if those around them are vaccinated.

I’m worried about my baby’s shots. Are vaccines safe?
Yes! Today’s vaccines are the safest in history. The Food and Drug Administration (FDA) tests new vaccines for up to 10 years before issuing the vaccine a license. All vaccines must be safe and proven to work well. Once the vaccine is being used, the FDA and the Centers for Disease Control and Prevention monitor it through the Vaccine Adverse Event Reporting System (VAERS). Researchers look for any problem with a vaccine, inspect the problem, and decide what to do. When VAERS found a problem in the past, changes included:

  • using different labels or packaging
  • sending safety alerts
  • inspecting manufacturers’ records
  • and taking away the vaccine’s license.

Sometimes vaccines can cause reactions like fever or soreness where the shot was given. Very rarely, people have an allergic reaction. Vaccines save lives and protect against the spread of disease. If you decide not to immunize your child, you put your child and other children around him or her at risk. Getting vaccinated is much safer than getting the disease.



Does the measles-mumps-rubella (MMR) vaccine cause autism?
No! Scientific data does not show a link between the MMR vaccine and autism. Autism is usually discovered when a child is 18 to 30 months. Children get the MMR vaccine just before this age, so some people believe that the MMR vaccine causes autism. These people often have wrong information. For example, in 1998, Andrew Wakefield published a small study saying that MMR caused inflammatory bowel disease and autism. Later, his results were rejected because the study had mistakes. Even his co-authors agreed that the results were wrong. No other studies can find a link between the MMR vaccine and autism. Because of the study, many British parents have refused to let their children get the vaccine. Now there are outbreaks of measles and mumps in areas where many children are not vaccinated. Other studies have been done, and none has found a link between MMR vaccine and autism. In 2004, a report by the Institute of Medicine Immunization Safety Review Committee again said that there is no link between autism and the MMR vaccine. Some parents still question vaccine safety because the media gives false claims a lot of attention, and the Internet has wrong information that is easy to find. Measles, mumps, and rubella are serious — protect your children by immunizing them at 12 to 15 months of age and again at 4 to 6 years of age.

I have read that the DTP vaccine can cause sudden infant death syndrome (SIDS). Is this true?
There is no scientific evidence that links the DTP (diphtheria, tetanus, pertussis) shot and SIDS. This myth continues because the first dose is given at 2 months of age, when the risk of SIDS is greatest. However, these events are not connected.



Why do we give our children so many shots? Is it safe to give multiple vaccines in one visit?
Vaccines are the best way to prevent diseases, which can cause pneumonia, meningitis, and even death. Children are given vaccines at a young age because this is when they are most likely to get the disease. If a child is not vaccinated and is exposed to a disease, the child’s body may not be strong enough to fight the disease. But an infant’s body can handle the small number of weakened and killed viruses in vaccines. The Centers for Disease Control and Prevention and the AAP recommend vaccination against 12 diseases. Because children need some of these vaccines more than once, children may receive up to 23 shots by the time they are 2 years old. A child may receive up to six shots during one visit to the doctor. Even though today children receive many shots, they are exposed to smaller doses of the killed or weakened viruses in vaccines. Studies and years of experience show that vaccines used for routine childhood immunizations can be safely given together, at one visit. The vaccines work just as well, and it does not increase the risk of side effects. The scientific data show that receiving multiple vaccines has no harmful effect on a normal child’s immune system. Talk to your pediatrician if you are concerned about the number of vaccines your child is scheduled to receive.



What is thimerosal? Is it safe?
Thimerosal is used in some vaccines and other medicines, including contact lens solutions, throat, and nose sprays. It stops bacteria and fungi from getting into open multi-dose vaccine containers. Thimerosal has a small amount of organic mercury in it. Some parents and others worry about a link between neurologic disorders and vaccines that use thimerosal. Reliable scientific studies have not shown that small amounts of thimerosal in vaccines cause harm, except for minor side effects like swelling and redness where the vaccine was given. In 1999, the Public Health Service and the AAP recommended that thimerosal be taken out of vaccines as a precaution. There is no evidence that thimerosal in vaccines is harmful, but children are exposed to different forms of mercury in the environment, such as in some fish. We can’t always remove the mercury from the environment, but we can control the mercury used in vaccines. So, by taking thimerosal out of vaccines, we lessen the amount of mercury a child will be exposed to early in life.
Since 2001, routinely recommended children’s vaccines being made in the United States (with some exceptions) contain no thimerosal or only trace amounts. Many childhood vaccines never used thimerosal, and some vaccines are only available with thimerosal, such as meningococcal vaccine, but they are not recommended for very young children.



Why are some of the other ingredients in vaccines? Are they safe?
Each ingredient has a specific function in a vaccine. These ingredients have been studied and are safe for humans in the amount used in vaccines. This amount is much less than children encounter in their environment, food, and water.

  • Aluminum salts. Aluminum salts help your body create a better immune response to vaccines. Aluminum salts are necessary to make some of the vaccines we use more effective. Without an adjuvant — a substance that helps increase the effectiveness of a vaccine — like aluminum, people could need more doses of shots to be protected. Everyone is exposed to aluminum because there is much aluminum in the Earth’s crust. It’s present in our food, air and water, and in breast milk and infant formula. The amount of aluminum in vaccines is similar to that found in 33 ounces of formula. Aluminum has been used and studied in vaccines for 75 years and is safe.
  • Formaldehyde. Formaldehyde is used to detoxify diphtheria and tetanus toxins or to inactivate a virus. The tiny amount that may be left in these vaccines is safe. Vaccines are not the only source of formaldehyde your baby is exposed to. Formaldehyde is also in products like paper towels, mascara, and carpeting. Our bodies normally have formaldehyde in the bloodstream and at levels higher than in vaccines.
  • Antibiotics. Antibiotics, such as neomycin, are present in some vaccines to prevent bacterial contamination when the vaccine is made. Trace amounts of antibiotics in vaccines rarely, if ever, cause allergic reactions.
  • Egg protein. Influenza and yellow fever vaccines are produced in eggs, so egg proteins are present in the final product and can cause allergic reaction. Measles and mumps vaccines are made in chick embryo cells in culture, not in eggs. The much smaller amount of remaining egg proteins found in the MMR vaccine does not usually cause a reaction in children who are allergic to eggs.
  • Gelatin. Some vaccines contain gelatin to protect them against freeze-drying or heat. People with severe allergies to gelatin should avoid getting gelatin-containing vaccines.


Do vaccines contain antifreeze?
No. Antifreeze is typically made of ethylene glycol, which is unsafe. Polyethylene glycol (a chemical used in antifreeze and personal care products like skin creams and toothpaste) is used in vaccines and is safe. It is used to inactivate the influenza virus in some influenza vaccines. It is also used to purify other vaccines.

Should vaccines be “greener”?
The amount of each additive used in vaccines is very small. In fact, we are exposed to much higher levels of these chemicals in our everyday lives. In vaccines, these ingredients are used to make the vaccine safer and more effective. Each vaccine is tested many times to make sure it is safe and works. Taking ingredients out might affect the ability of the vaccine to protect a child.



For more information about vaccines, visit these Web sites:

American Academy of Pediatrics:
MMR vaccine and autism:  or
Vaccine safety:
Vaccine Adverse Event Reporting System: or 800-822-7967
State laws: Immunization Action Coalition,

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