In the last week or so, I’ve done somewhere between 2 and 406 blog posts on vaccine risk perceptions (I am indeed bored beyond description; I feel obliged to reciprocate, though, the admirable efforts of others who are trying to shield public discourse from the harm associated with fact-free assertions in this area).

The upshot is that, contrary to the empirically uniformed and reckless blathering of “news” reporters and commentators (not all reporters or commentators are engaged in this behavior!), there is no meaningful public conflict over vaccine safety.

Not only have U.S. vaccination rates held steady at over 90%--the public health target—for all recommended childhood immunizations for over a decade.

But there is also overwhelming consensus in the general population, and within every recognizable political and cultural subsegment of it, that vaccines are safe and make a vital contribution to public health.

But these are characterizations of public risk perceptions.

Someone could—a commentator responding to one of my earlier posts did—reasonably ask about whether consensus on vaccine safety translates into consensus in favor of mandatory vaccination laws.

All U.S. states have such laws, requiring vaccination for mumps, measles, and rubella, along with various other childhood diseases, as a condition of school enrollment. All have so-called “medical exemptions,” for children who have a condition that would make vaccination unsafe, and most “religious” and some “moral” exemptions as well.

Can we say that the same state of consensus exists on this public health regulatory regime?

I’ll show you some data in a sec.

But because this post exceeds what the 14 billion regular readers of this blog know is my usually strictly enforced limit of 250 words, I'll start with this helpful and succinct summary of my own interpretation of them:

1. Yes, the same consensus supports the current state of the law on mandatory vaccination in the U.S. 2. However, pursuing legislation to change the status quo—either by eliminating religious or moral exemptions or by eliminating mandatory vaccination laws —risks polarizing the public along familiar political/cultural lines. 3. Launching childhood vaccines into the reason-eviscerating maelstrom of cultural status conflict that now characterizes issues like climate change, gun control, and the HPV vaccine would itself put this important aspect of our public health system in serious jeopardy. Accordingly, anyone who is considering initiating a campaign to change existing mandatory vaccination laws should (if they care about public health as opposed to making money by being employed to organize such a campaign; marketing and like consulting firms have a huge conflict of interest here) very carefully weigh the risk of that outcome against whatever benefits they might be hoping for in pursuing this course.

Okay. Here is the evidence.

1. Members of the nationally representative sample that participated in the CCP Vaccine Risk Perceptions and Ad Hoc Risk Communication study were asked what they thought of mandatory vaccination policies.

They responded to a series of questions, which are described in full in the Report,, after first being supplied information (also described there) that was materially identical to the information I supplied above about how those policies work and about the varying forms of exemptions that states permit. The questions were varied randomly in order.

By an overwhelming margin, the survey participants indicated that they favor existing laws.

Specifically, 75% (± 5% at a 0.95 level of confidence) indicated agreed that they “support leaving existing laws on childhood vaccinations as they are.”

What’s more, this was by far the dominant response across political lines:

The responses to this "let it be" item reflect exactly the same pattern that characterizes the general public’s responses to the study’s vaccine risk-perception items.

Indeed, I myself do not see the response to this item as measuring anything different from what the risk-benefit items measure.

Known as the “affect heuristic,” there is a strong tendency of people to form overall pro- or con- attitudes toward putative risk sources. Rather than a consequence of their assessment of evidence about those putative risks, their affective orientations are likely to shape how they interpret evidence and form beliefs (Slovic, Peters, Finucane & MacGregor 2005; Loewenstein, Weber, Hsee & Welch 2001).

One can ask them different questions and elicit responses that reflect people’s affective orientations toward one or another risk.

But that’s really all that one is doing with any of these questions: eliciting a generic pro-con attitude. It is in fact a mistake—one that non-scholarly opinion pollsters invite all the time to get attention or to try to manipulate public impressions of the public’s view on one or another policy issue—to try to take the wording of particular items at face value or to purport to draw inferences from one or another as opposed to all the items considered as a group.

The reactions of members of the public to childhood vaccines displays all the signatures of the affect heuristic.

Moreover, their affective orientation happens to be very positive in the vast bulk of the U.S. population. The CCP Report estimated that approximately 80% of the population shares it.

Like the risk-benefit questions generally, the CCP study "let it be" item on existing mandatory vaccine laws elicited a positive response of around 80%.

Like the risk-benefit items, there was not much in the way of systematic variance in the "let it be" item—that is, the reasons why somewhere around 20% or 25% of the population didn’t support existing laws did not admit of meaningful explanation by individual demographic or cultural or political characteristics.

Maybe these are the same 20% or so of the population who indicated that “space aliens” or “time travelers” were involved in the disappearance of Malaysian Airlines flight 370 last summer. No idea.

2. There is an important “however,” however.

Study participants were also asked to consider items relating to specific proposals to alter existing mandatory vaccination laws.

Their responses to these did not evince support consensus for change of any sort. Indeed, it revealed the striking absence of any particular consensus:

What's more, variance in the participants’ response did reflect differences in the participants’ political outlooks. Consider this Figure, which uses a multivariate model to estimate the impact of partisan differences, including identifying as a member of the Tea Party, on the responses to the reform items:

The figure illustrates how much more or less an average "liberal Democrat," "Conservative Republican, non--Tea Party member, or "Conservative Republican, Tea Party member" is to agree with the indicated reform than is the "average" member of the population--and hence how likely each of the former prototypical partisans is to disagree with each of the others.

These differences are modest in relation to those, say, on climate change. But they aren’t trivial.

Now what to make of this?

Well, if you are thinking there’s some inconsistency between the participants’ responses to these “change the status quo” items and their responses to the “let it be” item, I agree!

My view is that the “change the status quo” items are not measuring the same thing as the "let it be” item.

Psychometrically speaking, "change the status quo" items don’t “scale” with the “let it be” item or the general battery of risk-benefit items. That’s is, they don’t display the sort of covariance that one would expect if the items were measures of a common latent or unobserved disposition.

It makes more sense to view the "change the status quo" iems as measuring (in a noisy and attenuated form, particularly in relation, to say, climate change) the general attitudes that subjects of varying political outlooks have toward governmental regulations generally.

My view is that most people generally just don’t give much thought to vaccine laws, which (with the exception of the HPV vaccine; I’ll come back to that) have not been a matter of political contestation in American life.

So if one asks members of the public what they think of universal vaccination laws, they express the same warm fuzzy feeling of contentment and gratitude that characterizes their views toward childhood vaccines generally. These are the sensibilities, I'm confident, that for over a decade in US has lead 90%+ of parents to get all recommended childhood vaccinations for their kids.

Survey questions about changing those law, starts to trigger affective resonances that relate to peoples’ cultural identities. Like bad survey questions, those questions aren't measuring what people in society are talking about; but they are measuring something: who they are, culturally or politically speaking.

3. That's an outcome that ought to cause a sense of tremendous apprehension in anyone who actually values the contribution that childhood vaccines make to public health in this country.

The entanglement of issues of risk with antagonistic cultural meanings is precisely what drives polarization on issues like gun control and climate change, where people’s positions are understood to be badges of membership in and loyalty to opposing groups (Kahan 2015, 2012).

This was exactly the dynamic that generated polarization over the HPV vaccine, the only universally recommended vaccine that isn’t part of the schedule of mandatory, school-enrollment vaccinations across the U.S. states (Kahan et al. 2010).

I’ve written extensively, in this blog and elsewhere (Kahan 2013), about the sad career of the HPV vaccine.

But the basic point is that the HPV vaccine suffered this fate b/c its manufacture, Merck, decided to initiate a controversy-inviting nationwide legislative campaign to add the vaccine to the schedule of required vaccinations that states make a condition of school enrollment.

The company did so through what was initially a covert lobbying campaign that featured Governor “Oops” among others—the disclosure of which amplified the controversy the manufacturer was hoping to sidestep when it thrust the vaccine into the political process.

Merck didn’t have to do this. In the normal course, public health administrators, who are largely insulated from politics, would have almost certainly added the vaccine to their states’ requirements, as they had just finished doing for the HBV (hepatitis-b) vaccine, another STD immunization that was made mandatory for adolescents and then infants.

But the manufacture didn’t want to wait, because in extra time it would have taken to get such approval for a boys & girls vaccine added to the state mandatory lists by administrative action, a competitor, GlaxoSmithKline, would have obtained approval for a rival HPV vaccine and been able to compete for lucrative contracts with state school systems.

The risk that launching the HPV vaccine into the political process would disrupt people's ability to assess the risks and benefits of it was clear at the outset.

But Merck (for pefectly predictable, understandable reasons) decided to take a gamble, motivated by its desire to achieve a decisive commercial advantage in marketing the vaccine.

The company lost.

We all did.

Should we take a similar gamble by taking action that would place childhood vaccinations into the cross-hairs of partisan politics?

The CCP Report, which reported data similar to what I’ve just presented, discusses the considerations. I don’t see any point trying to reformulate the conclusion stated there:

In striking contrast to responses to the other items in the survey, the ones soliciting participants’ positions on proposals to restrict non-medical exemptions were characterized by disagreement. Not only did these items tend to divide the respondents. They divided them on political and cultural lines....

[T]hese results supply reason for circumspection on the issue of exemptions. The power of these items to divide groups already conspicuously arrayed against each other on contested science issues raises the possibility that real-world proposals to restrict universal immunization exemptions could do the same. The study’s experimental component, which found that exposure to the “anti-science” op-ed intensified these divisions, reinforces this concern....

Anyone who dismisses the existence or seriousness of unfounded fears of childhood vaccines would be behaving foolishly. Skilled journalists and others have vividly documented enclaves of concerted resistance to universal immunization programs. Experienced practitioners furnish credible reports of higher numbers of parents seeking counsel and assurance of vaccine safety. And valid measures of vaccination coverage and childhood disease outbreaks confirm that the incidence of such outbreaks is higher in the enclaves in which vaccine coverage falls dangerously short of the high rates of vaccination prevailing at the national level (Atwell et al. 2013; Glanz et al. 2013; Omer et al. 2008).

At the same time, only someone insufficiently attuned to the insights and methods of the science of science communication would infer that this threat to public health warrants a large-scale, sweeping “education” or “marketing” campaign aimed at parents generally or at the public at large. The potentially negative consequences of such a campaign would not be limited to the waste of furnishing assurances of safety to large numbers of people who are in no need of it. High-profile, emphatic assurances of safety themselves tend to generate concern. A broad scale and indiscriminant campaign to communicate vaccine safety—particularly if understood to be motivated by a general decline in vaccination rates—could also furnish a cue that cooperation with universal immunizations programs is low, potentially undermining reciprocal motivations to contribute to the public good of herd immunity. Lastly, such a campaign would create an advocacy climate ripe for the introduction of cultural partisanship and recrimination of the sort known to disable citizens’ capacity to recognize valid decision-relevant science generally .....

The right response to dynamics productive of excess concern over risk is empirically informed risk communication strategiestailored to those specific dynamics. Relevant dynamics in this setting include not only those that motivate enclaves of resistance to universal immunization but also those that figure in the concerns of individual parents seeking counsel, as they ought to, from their families’ pediatricians. Risk communication strategies specifically responsive to those dynamics should be formulated—and they should be tested, both in the course of their development and in their administration, so that those engaged in carrying them out can be confident that they are taking steps that are likely to work and can calibrate their approach as they learn more (Sadaf et al. 2013; Opel et al. 2012).

Again, preliminary research of this sort has commended. Perfection of behavioral-prediction profiles of the sort featured in Opel et al. (2011a, 2011b, 2013b) would not only enable researchers to extend understanding of the sources and consequences of genuine vaccine hesitancy but also to test focused risk-communication strategies on appropriate message recipients. If made sufficiently precise, screening protocols of this sort would also enable practitioners to accurately identify parents in need of counseling public health officials to identify regions where the extent of hesitancy warrants intervention.

The public health establishment should exercise leadership to make health professionals and other concerned individuals and groups appreciate the distinction between targeted strategies of this sort and the ad hoc forms of risk communication that were the focus of this study. They should help such groups understand in addition that support for the former does not justify either encouragement or tolerance of the latter.

But anyway, you've got the data now. Draw your own inferences -- from them, and not from the feral risk communication system that we rely on in this country to the detriment of our public health ....

References

Cultural Cognition Project Lab. Vaccine Risk Perceptions and Ad Hoc Risk Communication: An Emprical Analysis. CCP Risk Studies Report No. 17

Kahan, D. Why we are poles apart on climate change. Nature 488, 255 (2012).

Kahan, D., Braman, D., Cohen, G., Gastil, J. & Slovic, P. Who fears the HPV vaccine, who doesn’t, and why? An experimental study of the mechanisms of cultural cognition. Law Human Behav 34, 501-516 (2010).

Kahan, D.M. A risky science communication environment for vaccines. Science 342, 53-54 (2013).

Kahan, D.M. Climate-Science Communication and the Measurement Problem. Advances in Political Psychology 3 (2015).

Loewenstein, G.F., Weber, E.U., Hsee, C.K. & Welch, N. Risk as feelings. Psychological Bulletin 127, 267-287 (2001).

Slovic, P., Peters, E., Finucane, M.L. & MacGregor, D.G. Affect, Risk, and Decision Making. Health Psychology 24, S35-S40 (2005).