Thursday, May 15, 2014

Debunking Vaccine Myths

Debunking vaccination myths might not convince hesistant parents to vaccinate. In fact there's some evidence it actually might backfire. It's not news that people cling to their beliefs, even refuted, contradictory or irrational ones but a recent study in Pediatrics of over 1,700 parents had a surprise twist. Fact-based information about the refuted link between vaccines and autism strengthened the stance of anti-vax parents. As odd as it might seem, debunking appeared to make the least-likely-to-vaccinate even less likely to vaccinate. Let's take a closer look.

Parents were randomly assigned to get one of these fun-filled messages:

Does this photo make you fear vaccines? Credit: CDC via NBCNews
1) information explaining the lack of evidence that MMR causes autism from the Centers for Disease Control and Prevention; (i.e. the DEBUNKING)

(2) textual information about the dangers of the diseases prevented by MMR from the Vaccine Information Statement; (i.e. DISEASE FACTS)

(3) images of children who have diseases prevented by the MMR vaccine; (i.e SICK KID)

(4) a dramatic narrative about an infant who almost died of measles from a Centers for Disease Control and Prevention fact sheet. (i.e. SAD STORY) via Pediatrics

Which one was the most effective in boosting parental motivation to vaccinate?

None of the above. 

Not a single message made parents more likely to report they'd "vaccinate a future child." In general 90% vaccinate on schedule so there's not much wiggle room for improvement. But as I said earlier, debunking (#1) made hestitant parents less likely to report they'd vaccinate. The percentage of wary parents who indicated they would vaccinate fell from 70 to 45.

Here's the wacky part. Even though debunking (#1) lowered intent to vaccinate among worried parents, at the same it also appeared to correct false beliefs about a MMR/vaccine link, even among the hesitant crowd. Here's how lead author Brendan Nyhan explained it:

The problem in this case wasn’t getting parents to believe the facts. Our results indicate that parents who saw the corrective information were less likely to believe in the vaccines-autism myth than those who didn’t. It seems that raising the topic may have instead prompted skeptical parents to think of other concerns or hesitations they have about vaccines to defend their views on the topic. via New York Times
There's even more bad news. 

Parents who saw the photos of sick children were more likely to believe the MMR caused autism. 

Parents who read about a sick kid were more likely to believe vaccines were not safe.

Those are not typos.

Encountering sick children fuels anxiety and thus fears about illness and vaccines and children.  A cognitive or social psychologist might say sick kids activate or "prime" the "illness" mental construct, the cerebral warehouse for all illness information. Look at the photo over there. It's making me very uncomfortable, how about you? It's long been known that fear-based messages not only do not work but backfire in public health. 

A few caveats here. This was a "web-based study" so parents did a survey online and read the vaccine info online. They weren't actually in the pediatrician's office deciding whether to vaccinate. Some had children much older than the typical vaccination ages. And unlike the real world, they didn't get the full vaccination spiel, just a single component. Typically parents would hear facts about the disease, the refuted MMR/vaccine link, vaccine safety info, and maybe a cautionary tale. 

Given these results I wasn't altogether surprised to read vaccination rates didn't rise after the pertussis outbreaks in the state of Washington.

Obviously there's a fine art and science to crafting public health messages. I'm not going to throw out the debunking quite yet though. If nobody bothers correcting misinformation it just stays out there. Hangs out in the media. Attracts celebrities.

And eventually its own band. 

Who knew there was a vaccine protest band? The Refusers. Now you won't learn that in Pediatrics or even Science Daily. You have to go to the mainstream media, here a well-written NBC article, to find that kind of scoop. 



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