Why there's no dispelling the myth that vaccines cause autism.

Previously published Slate articles made new.
Feb. 2 2010 1:56 PM

True Believers

Why there's no dispelling the myth that vaccines cause autism.

Mad Science: As Seen on TV. Click image to expand.
An autistic blogger's parody magazine cover

On Tuesday, the medical journal the Lancet retracted a 1998 paper that linked the MMR vaccine to autism. The controversial paper was challenged and debunked by the scientific community, but it nevertheless sparked a panic among many parents. In 2007, Arthur Allen explained why scientists are unlikely to convince the parents of autistic children that vaccines are not to blame. The original article is reprinted below.

At the recent 12-day hearing into theories that vaccines cause autism, the link between the disorder and the measles-mumps-rubella vaccine came across as shaky at best. As for the mercury-containing preservative thimerosal, which was used in other vaccines, witnesses showed that in all known cases of actual mercury poisoning (none of which caused autism), the dose was hundreds or thousands of times higher than what kids got during the 1990s. Powerful population studies showed no link to either MMR or thimerosal-containing shots.

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None of that moves Mary Wildman, 47, whose son's case is before the court and who drove from her home near Pittsburgh to watch the hearing, which ended this week. "I know what happened to my son after he got his MMR shot," she told me. "I have no doubt. There's no way they'll convince me that all these kids were not damaged by vaccines."

It is difficult to challenge a mother's knowledge of her own child. And also to fight off the staying power of the vaccines-cause-autism theory and other such notions that verge on the irrational.

People who study irrational beliefs have a variety of ways of explaining why we cling to them. In rational choice theory, what appear to be crazy choices are actually rational, in that they maximize an individual's benefit—or at least make him or her feel good.

Blaming vaccines can promise benefits. Victory in a lawsuit is an obvious one, especially for middle-class parents struggling to care for and educate their unruly and unresponsive kids. Another apparent benefit is the notion, espoused by a network of alternative-medical practitioners and supplement pushers, that if vaccines are the cause, the damage can be repaired, the child made whole. In the homes of autistic children it is not unusual to find cabinets filled with 40 different vitamins and supplements, along with casein-free, gluten-free foods, antibiotics, and other drugs and potions. Each is designed to fix an aspect of the "damage" that vaccines or other "toxins" caused.

"Hope is a powerful drug," says Jim Laidler, a Portland scientist and father of two autistic boys who jumped ship from the vaccine conspiracy a few years ago. In reality, autism has no cure, nor even a clearly defined cause. Science takes its time and often provides no definitive answers. That isn't medicine that's easy to swallow.

Another explanation for the refusal to face facts is what cognitive scientists call confirmation bias. Years ago, when writing an article for the Washington Post Magazine about the Tailwind affair, a screwy piece of journalism about a nonexistent attack on American POWs with sarin gas, I concluded that the story's CNN producers had become wedded to the thesis after interviewing a few unreliable sources. After that, they unconsciously discounted any facts that interfered with their juicy story. They weren't lying—except, perhaps, to themselves. They had brain blindness—confirmation bias.

The same might be said of crusading journalists like David Kirby, author of Evidence of Harm, a book that seemed to corroborate the beliefs of hundreds of parents of autistic children, and UPI reporters Dan Olmsted and Mark Benjamin (the latter now with Salon).

Systems of belief such as religion and even scientific paradigms can lock their adherents into confirmation biases. And then tidbits of fact or gossip appear over the Internet to shore them up. There's a point of no return beyond which it's very hard to change one's views about an important subject.

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