What about serious side effects? How often do they occur, and should you worry about them? This is an issue that has been studied repeatedly and intensively. Here are some facts that should help put your mind at ease.

Yes, there are reports of serious side effects that have been blamed on vaccines. But proving that the vaccine caused these side effects is often hard to do. In many cases, children simply develop illnesses around the time they’ve received a vaccine, and the immunizations get blamed unfairly. Don’t forget that infants and children are given vaccinations at a time in life when certain health conditions begin and become apparent to both parent and doctor. In most cases, the evidence just isn’t there to support a cause-and-effect link with vaccines.

That’s the case with the myth linking the diphtheria-tetanus-pertussis (DTP) vaccine with sudden infant death syndrome (SIDS). The first dose of the vaccine is administered when a baby is 2 months old, which coincides with the time of life when the risk of SIDS is highest. Thus, you would expect some SIDS deaths to occur in this age group, whether children receive the immunization. In fact, a number of studies dating back to the 1980s looked at the incidence of SIDS deaths occurring at the time of the DTP vaccine. The researchers concluded that the number of deaths was at a level about equal to the number that would be expected to take place by chance. In short, there just isn’t any scientific evidence linking the vaccine with SIDS. Even so, many of the myths surrounding vaccines seem to have a life of their own. Below, you’ll find a description of some of these unfounded claims, as well as a look at what the scientific evidence shows.

Measles-Mumps-Rubella Vaccine and Autism
Autism is made up of many chronic developmental disorders and is often first diagnosed in toddlers. The number of cases of autism is reportedly on the rise, and some critics insist that the measles-mumps-rubella (MMR) vaccine is to blame. Others say the increase can be attributed to better reporting of autism cases by doctors. In 2001 and again in 2004, the Institute of Medicine (IOM) Immunization Safety Review Committee, an independent body of experts who have no conflict of interest with pharmaceutical companies or organizations that make vaccine recommendations, studied a possible MMR-autism link and found no evidence supporting such a connection. A panel of experts brought together by the AAP reached the same conclusion. Most of the authors of the original study linking MMR to autism have retracted their support of the study.

Risks of Thimerosal?
Since the 1930s, some vaccines have included a mercury-containing preservative called thimerosal. It has been used as an additive to vaccines because of its ability to prevent contamination by bacteria or fungi. Critics have argued that thimerosal-containing vaccines are the cause of a number of neurologic and developmental disorders, ranging from autism to attention-deficit/hyperactivity disorder and speech and language delays. The IOM safety committee studied this issue and concluded that the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism. Since the end of 2001, most of the vaccines recommended by the AAP are available in thimerosal-free formulations. Some vaccines, such as the MMR, polio, and chickenpox vaccines, have never contained thimerosal.

Multiple Immunizations and Immune Disorders
Because some immunizations are given together, parents are often concerned that multiple vaccines might trigger health problems associated with the immune system. Can they increase your child’s risk of infections? Can they lead to the development of type 1 diabetes or various allergic diseases including asthma? After looking at this issue, the IOM committee concluded that there is no evidence of a cause-and-effect relationship between multiple immunizations and a greater risk of infections and/or type 1 diabetes. As for a link with asthma and other allergic disorders, there simply isn’t enough evidence to either accept or reject a connection with multiple vaccinations given together.

Hepatitis B Vaccines and Multiple Sclerosis
Although critics have claimed that hepatitis B immunizations can cause or trigger a relapse of multiple sclerosis, the IOM safety committee could find no scientific support for this theory. The same report also concluded that there is no evidence that the hepatitis B vaccine causes other types of nervous system problems, including Guillain-Barre

Why are preservative ingredients in vaccines?

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 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, including breast milk and formula. The amount of aluminum in vaccines is similar to that found in 33 ounces of infant 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 which 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 blood stream 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 (measles, mumps, rubella) vaccine does not usually cause a reaction in egg allergic children.

For more info on vaccine studies visit the AAP’s Healthy Children vaccine research page.