2007-06-30 Science on Trial/text

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Autism awareness has spread throughout the globe. Societies that never had a word for autism are inventing them, and autism societies are being founded on every continent. But while there is considerable agreement about how to define the signs and symptoms of autism, every society has their own ideas and beliefs about what causes it and how to treat it.

Autism has been linked to witchcraft in Africa, to poor mothering in France and South Korea, to divine blessings among some communities in Israel and India, and to measles in the United Kingdom. In most places, there are competing, co-existing systems of thought about autism, and the United States is no exception.

Over the last three weeks, I listened to testimony in the first of nine test cases in the U.S. Vaccine Court (Cedillo v. Health and Human Services) considering the question of whether a mercury-based vaccine preservative called thimerosal (which used to be in many vaccines), or the measles-mumps-rubella (MMR) vaccine, or both together caused autism in Michelle Cedillo, the plaintiffs' daughter.

I heard some of the world's leading experts on autism, immunology and vaccines testify that there is no biological model to account for an autism-vaccine connection, no scientific evidence or credible studies linking the two. They argue, instead, that autism is largely genetic.

And yet just last week, Robert F. Kennedy, Jr. wrote on the Huffington Post Web site that there are "hundreds of research studies" from dozens of countries providing "undeniable" proof that vaccines cause autism, and Rep. Dan Burton (R., Ind.) wrote a letter to the president of NBC claiming there was increasing evidence that thimerosal has contributed to an epidemic of autism. Scores of Web sites and autism advocacy groups are convinced of the connection, and the vast majority of scientists and physicians can't understand why. How is it possible that there could be two such contradictory explanatory models?

The judges presiding over Vaccine Court are being asked to believe in an elaborate set of arguments. To find for the plaintiffs, they will have to decide that the preponderance of the evidence suggests it is more likely than not that there is a true increase in the incidence of autism linked to the increase in numbers of vaccines children receive; that thimerosal can compromise the immune system; that the immune system would therefore be vulnerable to the measles vaccine virus; that the vaccine virus can cause a persistent infection in the gastrointestinal system, and the infection can cause autism -- and that all of these things occurred in the case of Michelle Cedillo.

The scientific testimony has been devastating to the plaintiffs because the recognized experts on autism, vaccines and immunology do not support even one of these premises, let alone a link between any of them. The only thing the government and the Cedillos agree on is that Michelle Cedillo has autism.

Scientists hope that a decision against the plaintiffs will slow down the antivaccine movement, and parent groups hope that a decision for the plaintiffs will prove that the government's vaccine program has poisoned a generation of children. My own view, as a parent of a child with autism, and as someone involved with epidemiological research on autism, is that neither vaccines nor anything ever contained in vaccines is related to autism or the increase in the prevalence of autism.

I base my opinion on scientific literature and no court decision is going to change it. Neither will a court decision change the minds of the antivaccine advocates. Two distinct communities have emerged, and though they both employ the language of science, their ideas are simply incommensurable. The two groups co-exist, like creationism and evolutionary biology, but they operate on such different premises that a true dialogue is nearly impossible. The plaintiffs, for example, are so convinced that the root of autism is to be found in mercury that they did not even call a single autism expert to the stand in a trial about autism.

Scientists are supported by an enormous network of publications and scientific agencies, but the antivaccine groups have their own support, mostly on the Internet. Spend just a few minutes browsing antivaccine chat groups and blogs and you will find widespread validation of the mercury-autism link, and a pronounced disdain for prestigious journals like Science, Nature and scientific peer review in general.

We should not expect too much out of this trial, or the next eight. The scientific community and antivaccine parent groups will each continue to look for clues under their own lampposts, because that is where the light is. But we should pay careful attention to this conflict. The antivaccine movement may be evidence that public confidence in science is eroding, which means that public health is at risk too.

Mr. Grinker, professor of anthropology and the human sciences at George Washington University and editor of the Anthropological Quarterly, is the author of "Unstrange Minds: Remapping the World of Autism" (Basic Books).