National Institute of Child Health & Human Development
Autism and the MMR Vaccine

Why do people think that vaccines can cause autism?

Some parents and families of children with autism believe that the Measles/Mumps/ Rubella (MMR) vaccine caused their children’s autism.These parents report that their children were “normal” until they received the MMR vaccine.Then, after getting the vaccine, their children started showing symptoms of autism.Because the symptoms of autism begin to occur around the same time as the child’s MMR vaccination, parents and families see the vaccine as the cause of the autism.However, just because the events happen around the same time does not mean that one caused the other.Although children receive many other vaccines in addition to the MMR vaccine, these other vaccines have not been identified as possible causes of autism.

These parents’ beliefs and observations were reinforced by a small study of bowel disease and autism, published by Wakefield and his colleagues in 1998 (Wakefield et al 1998).The study’s authors suggested that there was a link between the MMR vaccine and autism.This study did not include scientific testing to find out if there was a link.The authors relied on the reports of parents and families of the 12 children with autism involved in the study to make their suggestion. The study did not provide scientific proof that there was any link.

Since this study was published in 1998, a number of other studies have also been published that suggested a link between the MMR vaccine and autism (Singh et al 1998; Horvath et al 1999; O’Leary et al 2000; Wakefield et al 2000; Kawashima et al 2000), but none of these provide scientific proof of such a link.

To date there is no definite, scientific proof that any vaccine or combination of vaccines can cause autism.It’s important to know that vaccines actually help the immune system to defend the body.

How do vaccines help the immune system defend the body?

The immune system has cells, sometimes called memory cells, that remember diseases.If these cells meet a disease, they keep track of what it looks like so they can recognize it later.When the memory cells meet up with the disease again, they recognize it and know they need to get rid of it.They call in the other parts of the immune system to get rid of the disease.In some cases, memory cells can recognize a disease without ever having to meet up with it, which is called “natural” immunity.In other cases, the cells need some help to become familiar with a disease.

That help comes in the form of a vaccine.The vaccine takes a form of the disease that doesn’t make you sick and introduces it to the memory cells so they know what to look for later.If the memory cells ever bump into the disease again, they know to call in other cells in the immune system to protect the body and get rid of the disease.The memory cells of a child keep track of diseases well into adulthood, preventing such diseases by getting rid of them quickly.In this way, vaccines help the immune system by making it easier to remember diseases.

NICHD
Last Update: 08/15/2006