Science Panel Finds No Link Between Autism and MMR Vaccine

From the WebMD Archives

April 23, 2001 (Washington) -- A panel of independent experts has concluded that the measles, mumps, and rubella vaccine, or MMR, does not cause autism, a devastating brain disorder for which there is no cure. But the announcement by the 15-member committee convened by the National Academy of Sciences' Institute of Medicine (IOM) left the door open just a crack, which could allow the controversy surrounding the MMR vaccine to continue.

In its report released Monday, the IOM said that after considering evidence available today, it is reasonable to conclude that the vaccine does not cause autism. The scientists also said the evidence that does exist "shows no association" between the vaccine and the condition. Nonetheless, the panel could not rule out that MMR vaccine could contribute to autism in a small number of children.

One highly publicized and disputed 1998 British study brought suspicions about the vaccine to the forefront. It involved 12 children who had received MMR shots. They seemed to develop normally at first, but then developed bowel problems and regressed emotionally, exhibiting autism-like symptoms, such as bizarre ritualistic or repetitive behaviors.

Both the CDC and the National Institutes of Health asked the Immunization Review Safety Committee to evaluate the autism-MMR connection. The IOM committee then reached its conclusion about MMR and autism, which is similar to the conclusions made by the American Academy of Pediatrics and the World Health Organization.

After reviewing the existing literature, the panel could find no biological mechanism for the vaccine-disease relationship, nor could members justify the theory that a viral infection like measles, triggered by the vaccine, could produce bowel inflammation that may leak into a person's system and produce a kind of brain poisoning.

MMR vaccine supporters, however, are convinced of the benefits of the shot. They note that the three-in-one injection has virtually eliminated measles, mumps, and rubella in the U.S. For instance, measles cases dropped from about 400,000 cases a year to just 100 in 1999. However, in the developing world, where kids don't get the vaccine, measles may kill 1 million youngsters annually.

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Robert Davis, MD, MPH, of the University of Washington in Seattle, has recently published a study disputing the link between the MMR vaccine, bowel disease, and autism. He agrees with the IOM report's conclusion.

"In medical training, you have children like this die in your arms from these diseases, and once that happens, you realize that the vaccine actually prevents things that are very, very serious, and you never want to see it again," Davis tells WebMD. He says he worries that adverse publicity about the vaccine will cause parents to avoid it, which is happening right now in Great Britain.

Still, the idea already resonates among concerned parents: could the MMR vaccine -- a prerequisite of virtually all U.S. students to enter school -- pose an autism risk?

And on Capitol Hill, Chairman Dan Burton of the House Committee on Government Reform is planning hearings on the issue Wednesday and Thursday.

Burton (R-Ind.) has a 3-year-old grandson who developed autism shortly after getting an MMR shot, and the Congressman is a critic of U.S. vaccine policy.

"His concern remains. ... He wants to get to the bottom of this issue, because he's seen what's happened in his own family, and because as a chairman of an oversight committee, he wants to ensure the safety of the vaccine," Beth Clay, a committee staff member, tells WebMD.

While the IOM isn't recommending a change in a vaccine policy based on its report, it does say more research is warranted. Experts call for more studies that could identify currently unknown genetic or environmental risk factors that might lead to autism. Today, government-sponsored studies are trying to find out what happens to children who put off getting the MMR shot, as opposed to those who get it as early as possible.

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