Effects of pro- vs. anti-vaccine narratives on responses by recipients varying in numeracy

General Information

Effects of pro- vs. anti-vaccine narratives on responses by recipients varying in numeracy
Wändi Bruine de Bruin, Annika Wallin, Andrew M. Parker, JoNell Strough, and Janel Hanmer
Publication Type
Conference paper
Annual European conference of the Society for Medical Decision Making
Purpose: The Centers for Disease Control and Prevention (CDC) recommend flu vaccinations for almost all Americans over the age of 6 months. To inform patients’ vaccination decisions, health-care providers may share statistical evidence based on scientific studies and narrative evidence based on their experiences. Indeed, patients often welcome narratives describing other patients’ evaluations of their healthcare experiences. Narratives can provide pro-vaccine or anti-vaccine evaluative meaning that especially low-numerate patients struggle to derive from statistical information. However, concerns have been expressed (based on for example the social amplification of risk framework) that people could potentially perceive anti-treatment narratives as more informative than pro-treatment narratives.

For the present study, we designed narratives about flu shots, which differed in pro-vaccine and anti-vaccine evaluative meaning, but provided otherwise equivalent content. We examined whether the anti-vaccine (vs. pro-vaccine) narratives had stronger effects on judged vaccination probabilities due to being perceived as more informative, especially among recipients with lower numeracy.

Methods: We recruited 1113 participants from a US national internet panel. They were randomly assigned to a narrative that was (a) pro-vaccine or anti-vaccine, and (b) presented by a patient discussing a personal experience, a physician discussing a patient’s experience, or a physician discussing the experience of 50 patients. Pro-vaccine narratives described flu experiences of patients who got the flu after not getting vaccinated; anti-vaccine narratives described flu experiences of patients who got the flu after getting vaccinated. Each participant additionally received a standard CDC pamphlet with statistical information about vaccinations. Participants indicated their probability of getting vaccinated and how informative they perceived the narratives to be.

Results: Participants with lower numeracy rated narratives as being more informative, especially narratives that were anti-vaccine. Multi-mediation analyses suggested that low-numerate individuals’ judged probabilities of getting vaccinated were reduced by anti-vaccine narratives -- and to a lesser extent boosted by pro-vaccine narratives -- due to their perceiving narratives as more informative. These findings held whether narratives were provided by patients or physicians.

Conclusions: Health-care providers may add narrative information when presenting statistical evidence to inform patients’ decisions. However, as compared to high-numerate recipients, low-numerate recipients seem to rely more on such narrative information when making their decisions. We propose potential risk communication strategies for providing patients with the narratives they want, while correcting the differential sway of anti-vaccine narratives. Findings have implications for the development of health communications and decision aids.