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Thursday
Apr172014

Vaccine risk perceptions and risk communication: study conclusions & recommendations

From CCP's "Vaccine Risk Perceptions and Ad Hoc Risk Communication: An Empirical Assessment" report: 

II. Summary conclusions

A. Findings

1.   There is deep and widespread public consensus, even among groups strongly divided on other issues such as climate change and evolution, that childhood vaccinations make an essential contribution to public health. A very large supermajority believes that the benefits of childhood vaccinations outweigh their risks and that public health generally would suffer were vaccination rates to fall short of the goals set by public health authorities.


2.   In contrast to other disputed science issues, public opinion on the safety and efficacy of childhood vaccines is not meaningfully affected by differences in either science comprehension or religiosity. Public controversies over science, including those over evolution and climate change, often feature conflict among individuals of varying levels of religiosity, whose difference of opinion intensify in proportion to their level of science comprehension. There is no such division over vaccine risks and benefits.

3.   The public’s perception of the risks and benefits of vaccines bears the signature of a generalized affective evaluation, which is positive in a very high proportion of the population. The high degree of coherence in responses to items relating to the contribution that childhood vaccinations make to public health strongly implies that public assessments of vaccine risks and benefits reflect a unitary latent affective orientation. The distribution of that orientation is strongly skewed in a positive direction—indicating that a substantial majority of the population (in the vicinity of 75%) has a positive attitude toward childhood vaccines.

4.   Among the manifestations of the public’s positive orientation toward childhood vaccines is the perception that vaccine benefits predominate over vaccine risks and a high degree of confidence in the judgment of public health officials and experts. By large supermajorities, the survey participants endorsed the proposition that vaccine benefits outweigh their risks, and rejected claims that deterioration in vaccination coverage would pose no serious public health danger. They also expressed confidence in the judgment of officials who identify which vaccinations should be universally administered, and in the judgment of experts that vaccines are safe.

5.   Perceptions of the relationship between vaccines and specified diseases reflect the same positive affective orientation that informs public perceptions of the contribution that childhood vaccines make to public health generally. Responses to items on the link between vaccines and autism, cancer, diabetes—as well as a fictional disease not asserted by anyone to be connected to childhood vaccinations—displayed the same pattern as the responses to all the other public-health items. Under these circumstances, responses to these items can confidently be viewed only as indicators of the same latent affective attitude reflected in the public’s assessments of the contribution childhood vaccines make to public health generally. Public health officials should resist the mistake of construing responses to survey items such as these as measuring public knowledge about or beliefs on specific issues relating to childhood vaccinations.

6.   The demographic characteristics and political outlooks typically associated with group conflict over risk and related aspects of decision-relevant science are not meaningfully associated with disagreement about childhood-vaccination risks. Members of all such groups believe that vaccine risks are low, vaccine benefits high, and mandatory vaccination policies appropriate. Those who believe otherwise are outliers in every one of these groups.

7.   There is no meaningful association between concern over vaccine risks and the sharp cultural cleavage that characterizes perceptions of either “public safety risks,” a cluster of putative hazards associated with environmental issues and gun control, or “social deviancy risks,” a cluster associated with legalization of marijuana and prostitution and with teaching high school students about birth control. The opposing cultural allegiances that are associated with disputed societal and public health risks do not generate meaningful disagreement over vaccine risks and benefits. At most, such dispositions mildly influence the intensity with which culturally diverse members of the public approve of childhood vaccination.

8.   Existing universal vaccination policies appear to enjoy widespread support, but proposals to restrict existing grounds for exemption divide the public along partisan lines. Despite support for universal vaccination policies and widespread disapproval of parents who refuse to permit vaccination of their children based on concerns about vaccine risks, proposals to restrict or eliminate moral or religious grounds for opting out of vaccination requirements provoke dissensus along largely partisan lines consistent with citizens’ general orientation toward government regulation.

9.   The public generally underestimates vaccination rates and overestimates the rate of exemption. Only 9% of the survey respondents recognized that the vaccination rate among U.S. children aged 19-35 months for recommended childhood vaccinations has been over 90% in recent years. The median estimate was between 70-79%. The median estimate of children receiving no vaccinations was 2-10%; only 9% correctly indicated that less than 1% of children aged 19-35 months receive none of the recommended childhood vaccinations.

10.  Communications that assert the existence of growing concern over vaccination risks and declining vaccination rates magnify misestimations of vaccination rates and of exemptions. Experiment subjects who read communications patterned on real media communications underestimated vaccine coverage by an even larger amount than subjects in the control.

11.  Communications that connect “growing concern” over vaccine risks to disbelief in evolution and climate change generate cultural polarization. Relative to their counterparts in a control condition, experiment subjects exposed to such a communication divided along lines that reflected their predispositions toward currently disputed societal risks.

12.  Factually accurate information on vaccine rates, when issued by the CDC, substantially corrects underestimation of vaccination rates. Exposure to a story patterned on the press statements that the CDC typically issues in connection with annual NIS updates resulted in a significant correction of experiment subjects’ underestimation of national vaccination coverage.

B. Normative and prescriptive conclusions

1.   Risk communicators—including journalists, advocates, and public health professionals—should refrain from conveying the false impression that a substantial proportion of parents or of the public generally doubts vaccine safety. Such information risks creating anxiety rather than dispelling it. Moreover, by aggravating underestimation of vaccination rates, communications of this nature obscure a signal that conveys public confidence in vaccine safety and stimulates reciprocal motivations to contribute to the collective good of herd immunity.

2.   Risk communicators should avoid resort to the factually unsupportable, polemical trope that links vaccine risk concerns to climate-change skepticism and to disbelief in evolution as evidence of growing societal distrust in science. Such rhetoric, in addition to being facile, risks generating an affective or symbolic link between vaccines and issues on which cultural polarization is currently a significant impediment to public science communication.

3.   Risk communicators, including public health officials and professionals, should aggressively disseminate true information on the historically and continuing high rates of childhood vaccination in the U.S. The high levels of vaccination in the U.S. are a science communication resource. That resource should be exploited, not obscured or dissipated.

4.   Because there is a chance that it would make mandatory vaccination policies a matter of partisan contestation, campaigns to promote legislative elimination or contraction of existing grounds for exemptions should be viewed with extreme caution. There is reason to believe—from real-world experience as well as the results of this study—that proposals to restrict nonmedical exemptions from existing mandates would generate partisan division in the public. As evidenced by the controversy over the HPV vaccine, such divisions disrupt the processes by which ordinary citizens recognize and orient themselves with respect to the best-available evidence on public-health and other risks. Accordingly, the potential for creating polarization over childhood vaccination risks is a cost that must be balanced against whatever benefit might be obtained from reforms in law aimed at reducing the already very low percentage of parents that exempt their children from mandatory vaccination.

5.   Vaccine-risk assessments and communication should not be based on creative extrapolations from general theories. Because decision-science mechanisms can be imaginatively manipulated to support a wide variety of explanations and prescriptions, it is a mistake to present theoretical syntheses of work in this field as a guide for action. Instead, conjectures informed by decision-science frameworks should be treated as hypotheses for empirical investigation.

6.   Hypotheses relating to vaccine-risk perceptions and vaccine-risk communication should be tested with valid empirical methods specifically suited to measuring matters of consequence. Opinion polls cannot be expected to generate significant insight into vaccine risk perceptions, either on the part of parents, whose responses are unreliable indicators of behavior, or the general public, in whom demographic and attitudinal measures fail to explain practically meaningful levels of variance. Rather, behavioral measures (including validated attitudinal indicators of behavior) should be used to gauge parental risk concern and fine-grained, local methods used to investigate the characteristics of enclaves of demonstrated vaccine hesitancy.

7.   The public health establishment should take the initiative to develop comprehensive proposals for better integrating the science of science communication into its culture and practices. Procedures should be adopted, within government public health agencies and within the medical profession, for making use of the best available empirical methods for anticipating and averting influences that distort public risk perceptions. The public health establishment should also propagate professional norms geared to curbing ill-informed and ill-considered forms of ad hoc risk perception by the media and by individual members of the public-health establishment. The most effective step to discouraging this form of feral risk communication is to populate the niche it now occupies with an empirically informed and systematically planned alternative.

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