15 Things You Need to Know About Vaccines

Experts answer common questions about vaccines for children and adults.

 

Do Vaccines Cause Side Effects?

“All vaccines can cause mild side effects,” says Offit. Those side infects can include pain and tenderness at the site of an injection, a low-grade fever, and irritability. The chicken pox and measles vaccines sometimes provoke a mild rash that looks like a few blisters or spots. In addition, vaccines can sometimes cause a high fever in children, which can lead to a febrile seizure (this type of fever-caused seizure is harmless, but it can be very scary for parents). Other side effects are much more rare, though they can happen: The oral polio vaccine that used to be given in the United States did, in a few instances, actually cause polio, but the shot that is used today does not. Measles can cause a lowering of a child’s platelet count, but it does not last or cause permanent problems, says Offit.

Is There Evidence of a Connection Between Vaccines and Autism?

“Dozens of studies have been done and none have shown a connection between vaccines and autism,” says Allison Singer, president of the Autism Science Foundation. A possible connection was first raised by Dr. Andrew Wakefield, a British doctor who published a study in 1998 of 12 children in Britain who were diagnosed with autism within a month of receiving the MMR vaccine.

Wakefield’s paper “has since been withdrawn by the scientific journal that published it. It was declared to be fraudulent, and the primary author was stripped of his medical license,” says Singer. “Studies have been conducted all around the world to try to replicate Wakefield’s data,” says Amy Pisani, executive director of Every Child by Two, an organization that raises awareness about the importance of timely immunizations, “and there’s never been a single study connecting vaccines and autism. Of all the things we know about autism, we know vaccines do not cause it.”

What Is Thimerosal and Is It Dangerous?

The mercury-containing preservative thimerosal, which keeps vaccines sterile, is an ingredient in vaccines that are used to inoculate more than one person at a time (such as the flu vaccine). Mercury is a heavy metal that can be damaging in high doses, which is why concerns were raised about a possible connection between vaccines containing thimerosal and autism. Since the late ’90s, seven large studies have been done in the U.S., Canada, and Europe comparing children in Europe (where thimerosal was banned in 1991) and the United States (where it remained in most vaccines until 1999). The result? “You were not at greater risk for autism if you got a vaccine with thimerosal than if you didn’t,” says Offit. These days, thimerosal is in very few vaccines in the U.S. and, Offit says, children are exposed to much higher levels of mercury from the environment alone (for instance, breast-fed babies are exposed to more mercury from breast milk than were children who received vaccines before thimerosal was removed in 1999, says Offit). In addition, the type of mercury used in vaccines (ethylmercury) is actually eliminated from your body much faster than the type found in the environment (methylmercury). Still, if you’re concerned about thimerosal, it is possible to ask your pediatrician for thimerosal-free vaccines.