Debunking Vaccine Myths Can Have An Unintended Effect

Remember back in October when I debunked 32 myths about the flu vaccine here?

Research published since then suggests my efforts might have been in vain, at least in part.

The post might have changed some minds, but it seems unlikely to have led legions of people to race to get vaccinated.

In fact, people concerned about flu vaccine side effects may have been less likely to get the shot after reading the piece, even if it convinced them that the myths were false.

Yes, you read that right. The study, published Monday in the journal Vaccine, found that countering a big misperception about flu vaccines — that they can give you the flu (No. 6 on the list) — had a surprising effect. Education reduced misbelief, but it also reduced the likelihood that people already uneasy about the vaccine would plan to get it.

"There's a temptation to believe that communication is a silver bullet," said Brendan Nyhan, the Dartmouth researcher who conducted the study with Jason Reifler of the University of Exeter. "Our research suggests that's the wrong way to think about this. People's minds aren't that easily changed."

Because researchers can't look into people's heads, they test what influences may lead someone to get or avoid a vaccine. "We were interested in whether people believing the flu vaccine can give you the flu is the reason they're not getting the vaccine and whether correcting people's misperceptions would make them more likely to get it," Nyhan said. "The answer is no."

Nyhan and Reifler randomly split 1,000 people into three groups and asked them how concerned they were about serious side effects from vaccines, thereby identifying those "very" or "extremely concerned" about vaccines generally (24 percent overall, divided about equally across the three groups).

Then, the researchers gave one group information explaining the dangers of influenza and another group an explanation of how the flu vaccine cannot give someone the flu. The third group, the comparison group, received nothing. After the first two groups read the materials, the researchers asked them how likely it was they would get the flu vaccine this season, how safe they believed it is for most people and how accurate it is to say someone can get the flu from the vaccine.

The debunking materials did appear to shift the needle on beliefs. Among those with high concerns about side effects, 70 percent in the comparison group believed they could get the flu from the vaccine compared with 51 percent who read the myth-buster. Among those with low concerns, 39 percent of the comparison group and 27 percent of those who read the debunking materials believed the misperception.

But actually planning to get the vaccine? That's another story: 46 percent of those with high concerns in the comparison group said they intended to get the vaccine. Yet only 28 percent of folks with high concerns who read the debunking materials said they might get one. And that's just their intention. "If you can't change their intentions, good luck changing their behavior," Nyhan said.

So what's going on here? It's probably not actually the misperception stopping people from getting the vaccine.

"If misperceptions cause vaccine hesitancy, then debunking those myths should increase willingness to vaccinate," Nyhan said. "But these results suggest that misperceptions about vaccines may be a reflection of less favorable attitudes toward vaccines rather than a cause."

One reason for this is "motivated reasoning," according to Melanie Tannenbaum, a Ph.D. candidate in social psychology who studied persuasion at the University of Illinois, Urbana-Champaign. Motivated reasoning is the psychology concept that explains why people move the goalposts in an argument.

"Even if you address specific misperceptions, our motivated reasoning system is going to jump in to fill in the gaps," Tannenbaum said. "We do a lot to protect the beliefs we already hold, and if one aspect of that belief is challenged, it is easy enough to fill in other reasons."

So then, is there no point in countering all the misinformation out there, as I did with that previous myth-busting post? Not necessarily.

"I think there's still value in putting the accurate information out there because, for the more casual reader, you don't want them seeing only the wrong information and thinking that must be right because that's all that exists," Tannenbaum said. "Even if you're not succeeding in convincing every person who reads it, on a macro level you're making sure that the correct information is available in as much quantity as the misinformation."

Further, Nyhan said his research is aimed at public health officials whose goal is to increase vaccine uptake, a different goal than mine, as a journalist providing accurate information. And motivated reasoning kicks in primarily with topics people feel strongly about, Nyhan said. "When you ask people about things they don't care about, they're very happy to accept corrective information," he said.

Still, in this study, even those with low concerns were no more or less likely to get the vaccine after reading the corrective information. And Nyhan pointed out that a possible weakness of our approach was stating myths in the first place: some past research has found that exposure to the myths — even for the sake of debunking them — creates an "illusion of truth" that may reinforce the incorrect beliefs.

The problem is that there aren't many effective alternatives yet. Research shows the source matters — people accept correct information about vaccines from trusted health care professionals in particular — but it's not clear what public health messaging might work.

"We know very little that's evidence-based about how to communicate about vaccines," Nyhan said. "We need to do a better job, whether it's journalists or educators or people in the health system, of providing accurate information about vaccines in a way that people will find persuasive, and we don't know how to do that yet."

Tara Haelle is a freelance health and science writer based in Peoria, Ill. She's on Twitter: @tarahaelle.