What do vaccines and the end of the world have in common? To some activists, it might seem like the former is going to bring about the latter. To the rest of us, there may be a more subtle connection.

A new article in the NEJM examines the characteristics of families that refuse vaccination. Chris Mooney blogs about it at The Intersection, noting that the families that refuse vaccination tend to seek medical information from a tightly interconnected community of alternative healers and anti-vaccination advocates, rather than relying on the scientific or medical establishment.

Mooney also has a piece in Discover about why the vaccination-autism controversy persists. I was particularly struck by this passage:

Meanwhile, in the face of powerful evidence against two of its strongest initial hypotheses—concerning MMR and thimerosal—the vaccine skeptic movement is morphing before our eyes. Advocates have begun moving the goalposts, now claiming, for instance, that the childhood vaccination schedule hits kids with too many vaccines at once, overwhelming their immune systems. Jenny McCarthy wants to “green our vaccines,” pointing to many other alleged toxins that they contain. “I think it’s definitely a response to the science, which has consistently shown no correlation,” says David Gorski, a cancer surgeon funded by the National Institutes of Health who in his spare time blogs at Respectful Insolence, a top medical blog known for its provaccine stance. A hardening of antivaccine attitudes, mixed with the despair experienced by families living under the strain of autism, has heightened the debate—sometimes leading to blowback against scientific researchers.

What this immediately reminded me of was Leon Festinger’s book When Prophecy Fails.

Festinger was a social psychologist who developed the theory of cognitive dissonance. WPF is an account of how Festinger and his colleagues infiltrated a cult that had predicted that the world would end on a specific day (December 20, 1954). He wanted to see what would happen when the predicted day came and went without incident.

Ordinary logic would suggest that if your theory makes an incorrect prediction, you should go back and question the theory. But what happened instead was that the disconfirming evidence actually strengthened the cultists’ beliefs. They decided that God had temporarily spared the world because of their dedication, and they became even more committed to trying to spread their views before the revised apocalypse date came around.

Drawing on cognitive dissonance theory, Festinger explained why the group’s beliefs were strengthened. Broadening beyond just cults, he outlined five conditions that will lead people to intensify their beliefs in the face of disconfirming evidence:

• The belief is deeply held
• The believer has taken public actions that reflect his/her commitment and that cannot be undone
• The belief leads to specific, falsifiable predictions about something that will happen
• The specific, falsifiable predictions are disconfirmed by objective evidence
• After the discomfirming evidence comes to light, the believer has social support from other believers

Under these conditions, Festinger argued, it is well near impossible to reverse the belief. You hold it too dearly, you’ve already committed yourself to it, and other people are telling you to hang in there. So instead, you try to figure out how you can twist or morph your belief in order to hold on to it.

Festinger’s account of these conditions and consequences does a strikingly good job of describing the arc of the vaccination-autism story. In the late 1990s, parents and activists became convinced that vaccines were causing autism. They developed two specific predictions. First, they proposed that the MMR vaccine triggered a release of toxins that had accumulated in the intestines; but the data failed to support this view and most of the scientists who first proposed it retracted the conclusion. Activists also argued that thimerosol (a preservative in vaccines that contains mercury) was responsible for the link; but when thimerosol was removed from most vaccines, autism rates didn’t go down. So now, as Mooney describes it, activists are once again “moving the goalposts.” They are now blaming other toxins or saying that vaccination schedules are at fault. The belief has morphed, but key elements of its original form are preserved (it’s something about vaccines), allowing them to feel like they haven’t been wrong.

Unfortunately, a broader casualty of this process is parents’ confidence in science and medicine. Festinger showed that disconfirming evidence didn’t just lead believers to believe more; it led them to proselytize more too. So now we face an increasingly outspoken group of sympathetic and passionate advocates telling parents not to believe scientists and doctors. And that undermined confidence has very real and dangerous consequences.

What should be done? Frankly, I’m not entirely sure. One problem, it seems to me, is how this debate is framed as “science” or “scientists” versus the anti-vaccine activists. Science is supposed to be the rules of the game and scientists the referees, not an opponent in it. But I’m not sure there’s any way around that. If one side doesn’t like where the rules lead to, who else are they going to blame?