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A Risky Science Communication Environment for Vaccines

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Empirically Informed Vaccine Risk Communication

Childhood vaccines deserve an investment in systematic, evidence based risk communication commensurate with the value that vaccines confer on society.

Today vaccine risk communication is neither systematic nor evidence based.

Rather it is dominated by the uncoordinated action of individual commentators—journalists, activists, and even some individual health professionals.  Their warnings of “growing crisis of confidence in vaccines” and resulting “erosion in immunization rates” is out of keeping with CDC data, which show that vaccination rates have persisted at or above 90%--the public health goal—for well over a decade, and that the proportion of children who receive none of the recommended vaccinations has remained below 1%.  Rather than “a large and growing number” of “otherwise mainstream parents” refusing to vaccinate their children, the CDC (2010) reports that “ ‘[n]early all parents are choosing to have their children protected against dangerous childhood diseases.’ 

As the CDC consistently cautions, however, there are enclaves where vaccination rates are much lower than the national average.  The size and duration of pertussis outbreaks are likely to be higher in such enclaves (Atwell et al. 2013; Glanz et al. 2013; Omer et al. 2008), as are periodic flare-ups of measles, a disease that has been eliminated in the U.S. but that is still occasionally imported from persons traveling abroad (CDC 2013a).

While not evidence of a “rising tide of vaccine hesitance,” low-vaccination enclaves are an unmistakable public health concern.

They admit of and demand careful empirical study aimed at identifying the influences that generate them, at measuring the impact they have on the incidence of childhood diseases, and at containing and eliminating them.

The misstatements of fact that characterize ad hoc risk communication promote none of these objectives. 

Indeed, far from addressing the dangers posed by enclaves of under-vaccination, the factual mischaracterizations that pervade these sources has the potential to generate both public confusion and conflict over vaccine safety.

This was the principal finding of the experimental component of the CCP’s Vaccine Risk Perceptions and Ad Hoc Risk Communication study.

The Report findings also have important implications about the form of empirical evidence that is most suited to identifying influences that generate unfounded concerns about vaccines and formulating risk-communication strategies for combatting them. 

General public opinion surveys are not likely to make a meaningful contribution to these aims. 

As the Study documents, general public attitudes are overwhelmingly positive and do not meaningfully vary across groups defined by characteristics such as race, education, religiosity, or cultural and political outlook.  The variance that general attitudinal measures can detect under these circumstances will necessarily be low and will characterize only practically unimportant degrees of intensity in support of vaccination. Misidentifying as hostile to universal vaccination groups whose members in fact support it creates confusion and resentment and does nothing to help practitioners and public health officials identify or counsel genuinely worried parents.

When parents’ views are measured in public opinion polls, moreover, the proportion who state that they have general concerns about vaccines will far exceed the proportion who display meaningful hesitancy (Opel et al. 2011b, 2013b).  Which ones are hesitant, moreover, cannot be reliably determined by survey measures because parental self-reports have been shown to be invalid indicators of their behavior in vaccinating their children.

To make a useful contribution to identifying genuinely vaccine hesitant parents and understanding their motivations, the empirical methods employed must be both targeted and behavioral

Researchers should focus on parents of children currently in the target age brackets for recommended childhood vaccinations. These are the individuals making decisions about childhood vaccination; how they understand vaccine risks can be reliably inferred from the attitudes of people who don’t have the same incentive they do to attend to information.

Moreover, researchers should, particularly at the outset of their research programs, be sure to focus their examination on populations in which the incidence of under-vaccination or outright vaccine refusal is known to be high in or der to enable a sufficiently large number of genuinely hesitant parents to be identified and compared to non-hesitant parents.

Finally, researchers must use valid behavioral measures. Self-report measures are not by themselves valid indicators of parents’ vaccination behavior. Accordingly,  the value of individual characteristics, including attitudinal measures, in formulating “vaccine hesitancy” screening instruments must be assessed by their power to predict actual behavior. 

For screening instruments to assist practitioners to identify hesitant parents, and researchers to test risk-communication materials, moreover, screening instruments will need to possess diagnostic precision at the individual level and not merely explanatory power with respect to population variance.

Research consistent with these recommendations is in fact underway (Opel et al. 2011a, 2011b, 2012, 2013).  Its  advancement is the key to acquiring the empirical knowledge necessary to protecting  from damage the science communication environment in which parents can reliably identify and evaluate the best available evidence on childhood vaccines (Kahan 2013).

The public health establishment should assure that this research gets the support and attention it deserves.

And it should help individual public health professionals, journalists, and others recognize that empirically uninformed, ad hoc risk-communication doesn’t promote the goal of preserving public confidence in childhood vaccines.



Atwell, J.E., Van Otterloo, J., Zipprich, J., Winter, K., Harriman, K., Salmon, D.A., Halsey, N.A. & Omer, S.B. Nonmedical vaccine exemptions and pertussis in california, 2010. Pediatrics 132, 624-630 (2013).

CDC, Measles—United States, Jan. 1-Aug. 24, 2013. Morbidity and Mortality Weekly Reports 62, 741-43 (2013a).

CDC. CDC National Survey Finds Early Childhood Immunization Rates Increasing. (Sept. 1, 2011), available at

CDC. CDC Survey Finds Childhood Immunization Rates Remain High. (Sept. 16, 2010a), available at

CDC. National, State, and Local Area Vaccination Coverage Among Children Aged 19–35 Months — United States, 2012. Morbidity and Mortality Weekly Reports 62, 733-740 (2013b).

Glanz, J.M., Newcomer, S.R., Narwaney, K.J., Hambidge, S.J., Daley, M.F., Wagner, N.M., McClure, D.L., Xu, S., Rowhani-Rahbar, A. & Lee, G.M. A population-based cohort study of undervaccination in 8 managed care organizations across the united statesundervaccination in us managed care organizations. JAMA pediatrics 167, 274-281 (2013).

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

Omer, S.B., Enger, K.S., Moulton, L.H., Halsey, N.A., Stokley, S. & Salmon, D.A. Geographic clustering of nonmedical exemptions to school immunization requirements and associations with geographic clustering of pertussis. American Journal of Epidemiology 168, 1389-1396 (2008).

Opel, D.J., Mangione-Smith, R., Taylor, J.A., Korfiatis, C., Wiese, C., Catz, S. & Martin, D.P. Development of a survey to identify vaccine-hesitant parents: The parent attitudes about childhood vaccines survey. Human Vaccines 7, 419-425 (2011a).

Opel, D.J., Robinson, J.D., Heritage, J., Korfiatis, C., Taylor, J.A. & Mangione-Smith, R. Characterizing providers’ immunization communication practices during health supervision visits with vaccine-hesitant parents: A pilot study. Vaccine 30, 1269-1275 (2012).

Opel, D.J., Taylor, J.A., Mangione-Smith, R., Solomon, C., Zhao, C., Catz, S. & Martin, D. Validity and reliability of a survey to identify vaccine-hesitant parents. Vaccine 29, 6598-6605 (2011b).

Opel, D.J., Taylor, J.A., Zhou, C., Catz, S., Myaing, M. & Mangione-Smith, R. The relationship between parent attitudes about childhood vaccines survey scores and future child immunization status: A validation study. JAMA pediatrics 167, 1065-1071 (2013)


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