A flu virus binds to cells in the respiratory tract. (Centers for Disease Control and Prevention)

It's never easy to convert someone who clings tightly to myths about some issue (see: climate change), but now comes research from Dartmouth College that in some cases the argument itself may be counter-productive.

Researchers there found that when they presented people with material explaining that the flu vaccine does not give you the flu, those with "high levels of concern about side effects were less likely to report that they would be immunized after seeing this information." That's true even though the explanations were generally effective at reducing belief in that myth and beliefs that the vaccine is unsafe.

The findings, published Monday in the journal Vaccine, build on previous research (some of it by the same author, Brendan Nyhan) that shows that providing accurate information about the MMR vaccine's perceived role in causing autism also reduced belief in that myth. But it still decreased the intention to vaccinate children among parents who viewed vaccinations least favorably.

"These results suggest that correcting vaccine myths may not be an effective approach to promoting vaccination," the authors concluded.

How to explain this seeming paradox? "Our explanation is that when you're challenged, you often try to defend the underlying belief or attitude that's come into question," said Nyhan, an assistant professor of government at Dartmouth. That's especially true when the issue is something a person cares deeply about. Anyone who has followed the vaccinate-or-don't-vaccinate debate knows that it qualifies.

"If misperceptions are the expression of a more generalized antipathy toward vaccines," the study notes, "then addressing these myths piecemeal is unlikely to be effective. A more comprehensive strategy is likely to be required."

But what would that strategy entail? One idea, Nyhan said, might be to have the information come from trusted community leaders, instead of from on high, i.e. from an already mistrusted government agency. Another might be to dispense with factual arguments and emphasize how vaccinating helps protect people an opponent cares about--his family, his friends, his neighbors.

Currently, there is little evidence-based research on vaccine messaging, Nyhan said. In the end, public health advocates may have to accept that while the vast majority of people in this country still vaccinate, some never will, Nyhan said.

"We have to be realistic," he said. "It doesn't mean we should give up hope."