Visitors follow Mickey Mouse for photos at Disneyland in Anaheim, Calif on Jan. 22. Seventy people have been infected in a measles outbreak that led California public health officials to urge those who haven’t been vaccinated against the disease, including children too young to be immunized, to avoid Disney parks where the spread originated. (AP/Jae C. Hong)

The dangerous problem of vaccine denial is getting more and more attention — thanks, sadly, to an outbreak of measles (an extremely contagious, vaccine-preventable disease) that began at Disneyland in southern California late last year.

At the same time, research is focusing on how clusters of people who don’t vaccinate their kids pose perhaps the greatest risk — a new study in Pediatrics finds that many of these clusters are in very politically liberal areas of California like “northern San Francisco and southern Marin County.”

Here’s the thing, though: We shouldn’t leap from this evidence to the assumption that refusing vaccinations is a special phenomenon driven by the ideology of the political left. There are also religious groups with low vaccination rates that have seen measles outbreaks, for instance, such as the Amish in Ohio and Orthodox Jews in Brooklyn — not groups that you could reasonably call “left wing.” And then, there’s rejection of the HPV vaccine in particular, which tends to be associated with the religious right.

Moreover, every time researchers examine the political outlooks of vaccine deniers through representative surveys, it seems that they fail to find a significant leftwing bent. Consider two major studies on this from the last two years:

* In a 2013 paper in PLOS One, Stephan Lewandowsky and two colleagues studied what makes people reject vaccines, and got a complicated result. Namely, they found that while political conservatism made people somewhat more pro-vaccine, having a free market ideology led in the opposite direction — towards having more vaccine skepticism.

“Opposition to vaccinations involved a balance between two opposing forces, namely a negative association with free-market endorsement and a compensatory positive association with conservatism,” wrote the authors. “The different polarity of those associations is consonant with the notion that libertarians object to the government intrusion arising from mandatory vaccination programs, whereas people low on conservatism — who, by implication, are liberal or progressive — may oppose immunization because they distrust pharmaceutical companies.”

But really, political ideology didn’t have a large overall impact on vaccine denial in the study. The study found that the really big contributor to distrusting or disliking vaccines was not political ideology ideology at all, but rather, having a conspiratorial mindset, which can occur on both the left and the right.

* In 2014, meanwhile, Yale’s Dan Kahan published results from a nationally representative survey which led him to conclude that the idea of vaccine fears being driven by leftwing ideology “lacks any factual basis.” In fact, Kahan found, “respondents formed more negative assessments of the risk and benefits of childhood vaccines as they became more conservative and identified more strongly with the Republican Party.” However, as in the prior study, this was a very slight effect.

Here’s a figure from Kahan’s paper, helpfully comparing how views of guns, climate change, marijuana legalization, and vaccines all shift as you move across the political spectrum. Views on vaccines show by far the least variability, compared with these other much more politicized topics:

Source: Dan Kahan.

Overall, then, this evidence suggests that while there may be some broadly leftwing motivations behind vaccine resistance — distrust of corporations that make vaccines, for instance, and fear that their products aren’t safe and that they can’t be trusted — there are also rightwing ones (e.g., distrust of the CDC and government that claims vaccines are safe). And on the national level, these influences may basically be a wash.

That doesn’t solve the puzzle of why so many clusters of the unvaccinated seem to pop up in leftwing places, like Marin County. While the relationship between national level polls (which seem to show anti-vax views appearing across the spectrum) and localized clusters isn’t fully clear, Dartmouth political scientist Brendan Nyhan, who has published a number of papers on the problem of vaccine rejection, points out one possible way out of the conundrum.

“We tend to think of areas with high exemption rates like Boulder or Marin as being liberal, but political liberalism is part of a correlated cluster of beliefs and lifestyles in those places and isn’t seemingly the most important explanatory factor in determining who’s a vaccine skeptic,” he notes.

In other words, we may be associating vaccine denial with liberalism when we see it in liberal places, but not recognizing that within those places, what makes a vaccine skeptic isn’t necessarily his or her liberal or leftwing politics.

The matter deserves more research, then. But one thing is clear — you can’t assert that distrust of vaccines is a problem exclusively or uniquely found on the left. The data just don’t support that.

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