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.

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.

Then, too, the material in discussion is highly technical and specialized, and most parents aren't truly able to determine which conclusions are reasonable. So they go with their gut, or the zeitgeist message that it makes more sense to trust the "little guy"—the maverick scientist, the alt-med practitioner—than established medicine and public health. "History tells us that a lot of ground-breaking discoveries are made by mavericks who don't follow the mainstream," says Laidler. "What is often left out is that most of the mavericks are just plain wrong. They laughed at Galileo and Edison, but they also laughed at Bozo the Clown and Don Knotts."

And to be sure, there was some basis for suspecting vaccines several years ago, before definitive studies had discounted a link. When the first vaccine theory was proposed in 1998, it appeared in the prestigious British medical journal Lancet and was published by an established London gastroenterologist, Andrew Wakefield. Two years later at a congressional hearing, Wakefield and an Irish pathologist and molecular biologist, John O'Leary, announced they had found measles viral RNA in the guts of autistic kids with severe bowel problems.

The air of respectability fell away over the years as we learned that Wakefield had serious conflicts of interest (including a 1997 patent application on a measles vaccine to replace the potentially soon-to-be-avoided MMR shot) and that a subsequent publication on measles RNA was probably an artifact of false positives, a common problem in polymerase chain-reaction technology.

The thimerosal theory emerged in a different context. The Centers for Disease Control and Prevention, concerned about cumulative mercury exposures in young children, asked manufacturers in 1999 to phase out thimerosal-containing vaccines. In other countries, such as Denmark and Canada, thimerosal was removed because of new vaccine combinations that either didn't require thimerosal or would be damaged by it. Nowhere was thimerosal removed because of evidence of harm.

But the first CDC study of children's exposures to thimerosal-containing vaccines was difficult to interpret. And anti-mercury activists jumped on the transcript of a 2000 meeting at which the study was scrutinized to argue that something improper was going on. The transcript shows no such thing. But the activists unleashed a public-relations campaign alleging a government and "big pharma" coverup.

That, in turn, proved to be eye candy for environmental groups already enraged by the Bush administration's enlistment of former industry officials in the squashing of environmental regulations. Anti-pollution lawyer Robert F. Kennedy zealously jumped on the thimerosal bandwagon in an "expose" published in Salon and Rolling Stone.

No surprise there. What editor or writer doesn't want to "reveal" that drugmakers and the government conspired to poison a generation of innocent kids. (Kirby's book won a 2005 Investigative Reporters and Editors award.) Where's the passion in the story that some public-health bureaucrats quietly moved to blunt a danger that turned out to be nonexistent?

In the pre-Internet days, the parents of an autistic child living in a small city might have found a handful of other parents in their predicament. Now, they instantly find thousands online. The denominator—healthy children—has disappeared. This is a good thing if you're looking for answers. But the answers may not be good ones. Joined together on the Internet, these actors create a climate of opinion that functions as an echo chamber for conspiracy dittoheads. Even the women's division of the Methodist Church has gotten in on the act, presumably on the grounds that it is fighting for social justice by decrying mercury poisoning, although there was no mercury poisoning, and social justice would be better met by promoting confidence in vaccines.

Kennedy, who wrote blithely in the Huffington Post during the trial that "overwhelming science" had confirmed the link, continues to believe it. So does Rep. Dan Burton, R-Ind., whose circuslike hearing room aired many such claims. Neither cites any solid studies, because they do not exist.

If and when the vaccine court rules against Michelle Cedillo, the 12-year-old autistic girl at the center of these first hearings, it won't change their minds. Long ago, the famous Dr. David Livingstone interviewed a rain doctor in Botswana. When Livingstone accused the rain doctor of being irrational or a cheat, the rain doctor replied, "Well, then there is a pair of us." If it rains, I take the credit, he said, and if your patient gets better, you take the credit. In neither case do we lose faith in our professions. You see, the rain doctor said, "what we believe is always more important than what actually happens.

Arthur Allen, author of Vaccine and Ripe: The Search for the Perfect Tomato, can be reached at artnews@earthlink.net.