3G-4 COMMUNICATING AMBIGUITY ABOUT VACCINE EFFECTIVENESS REDUCES VACCINATION INTENTIONS: AMBIGUITY AVERSION AND ITS MECHANISMS

Tuesday, October 25, 2016: 11:15 AM
Bayshore Ballroom Salon D, Lobby Level (Westin Bayshore Vancouver)

Paul K. J. Han, MD, MA, MPH1, Brian J. Zikmund-Fisher, PhD2, Aaron Scherer, PhD2, Megan Knaus, MPH2, Christine Duarte, PhD3 and Angela Fagerlin, PhD4, (1)Center for Outcomes Research, Maine Medical Center Research Institute, Portland, ME, (2)University of Michigan, Ann Arbor, MI, (3)Maine Medical Center, Portland, ME, (4)University of Utah / Salt Lake City VA, Salt Lake City, UT
Purpose: To assess the effects of communicating ambiguity about the effectiveness of influenza vaccination on the public’s vaccination intentions and related cognitions, and to explore mechanisms of these effects.

Method: 2701 Spanish participants completed an Internet survey after reading a hypothetical newspaper article describing a serious influenza epidemic in Spain, and advocating vaccination. Participants were randomized to 1 of 3 conditions varying in expressed ambiguity regarding the effectiveness of vaccination:  No Ambiguity, Ambiguity, and Normalized Ambiguity (accompanied by language reinforcing the routine, expected nature of ambiguity).  After reading their assigned scenarios, participants completed measures of vaccination intentions, influenza risk perceptions and worry, and perceived vaccination effectiveness, as well as individual differences in subjective literacy, optimism, and tolerance of uncertainty, ambiguity, and risk.  General linear models (MANOVA and ANOVA) adjusting for age, sex, and education were used to assess the effects of communicating ambiguity on both vaccination intentions and related health cognitions, and to explore potential moderators and mediators. 

Result: Vaccination intentions were significantly lower (p<0.0001) for both the Ambiguity (M=4.72, 95% CI: 4.57-4.87) and Normalized Ambiguity (M=4.66, 95% CI:  4.51-4.81) groups, compared with the No Ambiguity group (M=5.08, 95% CI:  4.93-5.24), consistent with the phenomenon of “ambiguity aversion.”  Subjective health literacy—but no other individual differences—moderated this effect; higher health literacy was associated with higher ambiguity aversion (more reduced vaccination intentions) for individuals in both the  Ambiguity and Normalized Ambiguity groups, compared to the No Ambiguity group (p=0.0015).  Overall, the Ambiguity and Normalized Ambiguity groups also demonstrated higher perceived severity of influenza, higher perceived influenza risk, higher influenza worry, and lower perceptions of the effectiveness of vaccination than the No Ambiguity group (p≤.01).  Perceptions of influenza severity and vaccination effectiveness mediated the negative effect of ambiguity on vaccination intentions.  

Conclusion: Communicating ambiguity about the effectiveness of influenza vaccination reduces vaccination intentions.  Ambiguity-normalizing language does not decrease this effect, and health literacy increases it; more literate individuals demonstrate greater ambiguity aversion.  The negative effect of ambiguity communication on vaccination intentions is mediated by its effects on perceptions of both the severity of the vaccine-preventable disease and the effectiveness of vaccination.  The mechanisms of ambiguity aversion in public health communication are complex, and greater understanding of these mechanisms may facilitate more effective management of this problem.

See more of: ORAL ABSTRACTS: DECISION BIASES, AFFECT AND INFORMATION PROCESSING

See more of: 38th Annual North American Meeting of the Society for Medical Decision Making