Nancy Brajtbord, left, administers a shot of Gardasil, a human papillomavirus vaccine, to a 14-year old patient in Dallas. (Jessica Rinaldi/Reuters)

In the recent political flare-up about vaccines, a persistent topic of debate is how attitudes toward vaccines are shaped by political ideology. Some research finds little association between perceptions of vaccine risk and political ideology — suggesting that vaccines are less politicized than many other scientific issues. But a recent survey also finds that a partisan gap has emerged since 2009 on the question of mandatory vaccinations.

We bring new data to bear on this question, drawing on an October 2014 YouGov survey conducted as part of the just-released Cooperative Congressional Election Study. Our results suggest that an erroneous belief in the link between vaccines and autism is most prevalent among conservatives.

In this survey, we asked people whether they agreed or disagreed that “there is a link between childhood vaccinations and autism.” People were also asked to place themselves on a seven-point scale ranging from liberal to conservative, to provide their party identification, and to answer a typical set of demographic questions. We also included four questions designed to measure people’s trust in government.

To characterize the link between ideology, party and beliefs about vaccines, we did two things. First, we examined whether the apparent effect of ideology was different among Democrats, Republicans and independents. Second, we examined whether ideology had a linear or non-linear relationship to beliefs. In particular, we tested the idea that strong ideologues — no matter whether liberal or conservative — are most likely to believe that vaccines may cause autism.

Below is the relationship between ideology and beliefs among Democrats, independents and Republicans.  This is based on a statistical model that also accounted for trust in government, income, education, age and race.


Graph by Robert Lupton and Christopher Hare. Source: 2014 Cooperative Congressional Election Study.

The probability of believing in a link between vaccines and autism is much higher among conservatives than liberals — regardless of whether people identified as Democrats, Republicans or independents. The apparent impact of ideology is most pronounced among political independents. There is no evidence that support for the vaccine-autism link is higher among strong liberals.

Ideology is not the only factor associated with beliefs about vaccines. Trust in government also plays a key role. The less people trusted the government, the more likely they were to believe in a link between vaccinations and autism. This was true among both Democrats and Republicans, although not independents. Today’s low levels of trust in government may, therefore, make people more susceptible to believing false claims about vaccines and autism.

That liberals are least likely to believe in a link between vaccines and autism might be surprising given well-publicized reports about low childhood vaccination rates in wealthy, liberal enclaves in states such as California. It may be that anti-vaccination liberals are quite rare and that their existence is mostly anecdotal. Or perhaps anti-vaccination liberals are widespread but are adept at masking their attitudes in surveys.

Although we cannot adjudicate between these possibilities, our findings do not suggest that anti-vaccination attitudes are concentrated on the left fringe. Instead, anti-vaccination attitudes appear concentrated among conservatives and those who distrust government.

Robert Lupton is a political scientist at Michigan State University. Christopher Hare is a PhD candidate in political science at the University of Georgia.

For more on this subject, see “News coverage of vaccine controversies drives down support for vaccines.”

Note: The survey was conducted as part of the 2014 Cooperative Congressional Election Study. The CCES was conducted by the survey firm YouGov in two waves last year — in October and November.  The sampling frame was American adults, and the sample size for this particular question about President Obama’s religion was 1,000.  Respondents were interviewed online. Further information about the YouGov sampling methodology is here, here and here.