Vaccines and Autism, or, Changing Minds is Hard

Some depressing research on attempts to convince parents that the MMR vaccine does not cause autism. The researchers identified a random group of about 2000 American parents:

They sent them one of four interventions to convince them that the MMR vaccine is safe, and that it’s needed. Which of these interventions worked best? None. Not one made it more likely that a parent might intend to give a future child a vaccine. When they gave evidence that vaccines aren’t linked to autism, that actually made parents who were already skittish about vaccines less likely to get their child one in the future. When they showed images of sick children to parents it increased their belief that vaccines caused autism. When they told a dramatic story about an infant in danger because he wasn’t immunized, it increased parents’ beliefs that vaccines had serious side effects. Basically, it was all depressing. Nothing was effective.

Once people have an association in their heads, like vaccines are dangerous, it is very, very hard to wipe out this assumed connection. In particular, if people are nervous, anything emotionally troubling only increases their nervousness. Besides this bit of research on vaccines, I have read that if you take people who are afraid of flying and show them pictures of car crashes, they only become more afraid of flying and more likely to drive instead.

UPDATE: Kevin Drum says this study reminds him of a passage from Othello:

But jealous souls will not be answer'd so;
They are not ever jealous for the cause,
But jealous for they are jealous: 'tis a monster
Begot upon itself, born on itself.