Why Do People Think the MMR Vaccine Causes Autism?

MMR, which stands for mumps/measles/rubella, is one of several live viral vaccines (chicken pox vaccine and the nasal flu vaccine are two others). It is routinely given at 12 to 15 months of age, which is coincidentally the age when autism is first likely to become evident.

Unlike the flu vaccine and a number of other childhood immunizations, the mumps/measles/rubella vaccine does not and did not contain thimerosal, a mercury-based preservative.

Parents with their baby girl at the pediatrician's office
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A Controversy Is Born

The concern over MMR began in 1992 when Dr. Andrew Wakefield, at that time an accredited British gastroenterologist, tested 12 youngsters with and without autism. According to a report based on that study, the findings uncovered a possible link between the measles virus in the gut and autism.

Researchers at Wakefield's Texas-based foundation called Thoughtful House claimed that:

"The child develops a leaky gut, tissue damage gets worse, the immune system grows weaker, and autoimmune reactions start. Then a lot of children experience a catastrophic event. Either in the form of a significant illness or a live virus vaccine. The immune system is overwhelmed and the child rapidly goes downhill.

Some parents report a gradual deterioration, but many children seem to develop autism after a particular event. They go into the hospital or they get an MMR shot and they’re never the same again. Autism is the end result of this developing series of reactions."

These claims have not been supported by any other studies including those that attempted unsuccessfully to replicate these results. Dozens of peer-reviewed epidemiologic studies showed no link between MMR and autism. In fact, Dr. Wakefield’s original study was completely discredited. Ten of the 12 authors withdrew their support from the article.

The CDC, the Institutes of Medicine, and other major research institutions looked into the issue and found that there was an enormous amount of evidence that there is no connection between the MMR vaccine and autism, and that there is no credible evidence that a link did exist.

But Why Autism at All?

Some studies have suggested, however, that autistic children do have more gastrointestinal problems. In addition, some research suggests that some kind of interaction between genetic predispositions and environmental issues may contribute to autism.

These studies, however, have not shown a causal link between MMR and autism. Meanwhile, many large international studies have found no link whatsoever.


In 2010, Wakefield resigned from Thoughtful House and the organization changed its name to The Johnson Center for Child Health and Development. This occurred almost immediately after Wakefield was stripped of his UK medical license for ethical violations.

All of these events, studies, and announcements, however, have not ended the belief that there is a link between vaccines and autism. Even outbreaks of measles in both the UK and the US as a result of withholding vaccines has not changed some minds. 

There have also been suggestions that research conducted by government agencies has been flawed or that evidence has been withheld from the public. Some MMR opponents claim that researchers who work for NIH and CDC come from and return to large pharmaceutical firms—and they and their firms have a great deal of money at risk.

Continued belief in an autism/MMR connection has been further spurred along by various celebrities, led by Jenny McCarthy, and by organizations built around Wakefield's legacy. While these organizations are still extant, they are far less active than they were back around the mid-2000's.

Interestingly, however, their cause has been taken up by some well-educated, well-to-do people and groups for whom a "clean" (chemical free) environment is believed to be a ticket to good health for themselves and their children.

A Word From Verywell

Despite ongoing research and emerging theories, little is fully understood about the cause or causes of autism itself. A combination of environmental factors and genetic predispositions may indeed play a significant role. But, the overwhelming weight of scientific evidence tells us that vaccines like MMR are not the culprit.

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Article Sources
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  1. Email Interview With Thoughtful House research staff, 2009.

  2. Chaidez V, Hansen RL, Hertz-Picciotto I. Gastrointestinal problems in children with autism, developmental delays or typical developmentJ Autism Dev Disord. 2014;44(5):1117–1127. doi:10.1007/s10803-013-1973-x

  3. Chaste P, Leboyer M. Autism risk factors: genes, environment, and gene-environment interactionsDialogues Clin Neurosci. 2012;14(3):281–292.

  4. Centers for Disease Control and Prevention. Science Summary: CDC Studies on Thimerosal in Vaccines.

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