Individuals on the conservative end of the political spectrum are less likely to vaccinate against preventable diseases than those more to the middle or left, according to a new study published by three professors from the University of Idaho.

The study, "The Influence of Political Ideology and Trust on Willingness to Vaccinate," by assistant professors Brent Baumgaertner, Juliet Carlisle and Florian Justwan of the College of Letters, Arts and Social Sciences explored social influences and the role they play in humans' protective behavior. It was published this week in the journal Public Library of Science One (PLOS ONE).

The effect of social influences on protective behavior are everywhere, Baumgaertner said. A sick employee wants to look tough to her boss, so she goes into work anyway. A person living in a Western culture does not wear a face mask to protect against disease, but a person in an Eastern culture might do the opposite.

In the case of vaccines in the U.S., the professors found an individual's political ideology appears to have an effect on whether they will seek out a preventive vaccination.

"We had a hunch to presume that conservatives would be less supportive of vaccines," Carlisle said.

But it took a series of interviews and collected data to prove that hypothesis right.

Interviewees were asked questions about their political beliefs, their attitudes about vaccinations and their demographic characteristics. That data was then compared to respondents' reactions to two hypothetical scenarios. In one, they had not yet received a vaccine for whooping cough, measles or influenza, but there was no immediate risk of getting infected. In another, they had not yet received the relevant vaccine, but there was an outbreak of the disease in their community. Respondents were asked to answer how likely they would be to get vaccinated in either situation.

According to the study, the responses indicated a strong statistical relationship, not just between political ideology and attitudes about vaccines, but between ideology and an individual's trust of government entities.

"In particular, more conservative respondents tend to express lower levels of trust in institutions like the (Centers for Disease Control and Prevention) than their less conservative counterparts," the study reads.

Carlisle explained, "Conservatives generally don't want government involved in their lives, so there is this ideological perspective that government is not good, whereas liberals generally want government intervention" and are likely more trusting of such behavior.

The data did disprove one of the professors' hypotheses - political ideology does not appear to have a strong relationship to how much an individual trusts their primary health care provider.

"What we find here is that it does matter very much which specific entity tells people about the risks and benefits of certain vaccines," Justwan said.

Primary health care providers, then, could be a neutral place for information on vaccines to be passed on to individuals, the professors said.

"If you know your audience is very skeptical of a health care institute, then it's probably better that this message doesn't come from them," Baumgaertner said.

The professors are now planning follow-up studies, one to explore how increased severity of symptoms affects a person's likelihood of receiving a vaccine, and another that would examine how exposure to certain media outlets affects a person's attitude about vaccines.

Taylor Nadauld can be reached at (208) 883-4630, by email to and on Twitter @tnadauldarg.

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