The hypothesis that vaccines cause autism has been about as thoroughly falsified through research as any health hypothesis can be. Even if, by bending over backward into a back-breaking contortionist pose to be “open-minded”, some people will concede that there’s still a bit of room for reasonable doubt about whether there is no link between vaccines and autism in “susceptible” populations, there is no room for reasonable doubt left over whether vaccines caused the so-called “autism-epidemic” of the last two decades. They did not. Similarly, the mercury-containing preservative thimerosal, which used to be in several childhood vaccines until the end of 2001, when thimerosal was removed from all but some flu vaccines, has been about as cleared of being a cause of autism as it is possible for a substance to be. Basically, if thimerosal-containing vaccines were a cause of autism, we would have expected to see a decrease in autism prevalence beginning three to five years after the removal of thimerosal. Epidemiological studies have failed to find such a decline and have also failed to find evidence of correlation. I realize that anti-vaccine activists argue that there are still trace amounts of thimerosal in some vaccines, but, even so, thimerosal exposure in children fell almost overnight to levels lower than the 1980s, which was before the beginning of the “autism epidemic.” At the very least, one would expect autism rates to fall back to 1980s levels if thimerosal in vaccines were a driving force behind this “epidemic.” They haven’t. Quite the contrary, they’ve continued to climb.
So why does the manufactroversy that vaccines cause autism persist? There is no longer a scientific controversy; by and large, the question has been asked and answered. Vaccines do not cause autism, as far as we can detect. True, it’s impossible to completely prove a negative hypothesis, but if there is any way that vaccines do cause autism, it’s at a level below the ability of large epidemiological studies with tens or even hundreds of thousands of children to detect. Yet the fear persists.
One reason is that it’s very hard to eradicate a false belief, once entrenched. I’ve discussed many times how difficult it is to change people’s minds, as motivated reasoning leads them to seek confirming evidence and discount all else. Disconfirming evidence can even lead people to harden their beliefs even more. In particular, the hardcore anti-vaccine activists who persist in spreading the vaccine-autism myth have an interest and motivation in this mythology at least as potent as the interest pharmaceutical companies have in defending vaccines—more so, arguably, given the emotional attachment people have for their children. After all, all pharmaceutical companies are interested in, according to this mythology, is profit. If a parent, correctly or incorrectly, somehow comes to believe that something or someone has hurt his or her child, it is among the most potent motivations known to do something about it.
Another reason is that the concept has become entrenched in our culture—or at least parts of our culture—to the point where it appears regularly in the media, thus reinforcing the idea among those who don’t pay attention to the issue or those who do but haven’t decided if they believe that vaccines cause autism that maybe there is something to fear. Maybe there is still a controversy. A perfect example appeared in The Baltimore Sun over the weekend entitled We don’t know enough about childhood vaccines and subtitled Researcher asks: Are 36 doses of vaccine by age 2 too much, too little, or just right? I contend that the editors of The Baltimore Sun, by publishing this anti-vaccine propaganda, which would have been at home on the websites of the anti-vaccine blog Age of Autism or on the website of anti-vaccine groups SafeMinds, Generation Rescue, the International Medical Council on Vaccination or the National Vaccine Information Center (NVIC). Examining this article, written by Margaret Dunkle, described as a “senior research scientist at the Department of Health Policy at George Washington University and director of the Early Identification and Intervention Collaborative for Los Angeles County” and as having “a family member who is vaccine-injured,” is what I would consider a “teachable moment” in analyzing the tactics of the anti-vaccine movement.