An (un)healthy social dilemma: a normative messaging field experiment with flu vaccinations

Abstract

Background Influenza seasons can be unpredictable and have the potential to rapidly affect populations, especially in crowded areas. Prior research suggests that normative messaging can be used to increase voluntary provision of public goods, such as the influenza vaccine. We extend the literature by examining the influence of normative messaging on the decision to get vaccinated against influenza. Methods We conduct a field experiment in conjunction with University Health Services, targeting undergraduate students living on campus. We use four posters, randomized by living area clusters to advertise flu vaccination clinics during the Fall. The wording on the posters is varied to emphasize the individual benefits of the vaccine, the social benefits of the vaccine or both benefits together. We collect survey data for those vaccinated at the vaccination clinics, and for those not vaccinated via an online survey. Results We find that any normative message increases the percentage of students getting the flu vaccine compared with no message. In terms of the likelihood of getting the flu vaccine, emphasizing both the individual and social benefits of vaccination has the largest increase in the vaccination rate (19–20 percentage point increase). However, flu vaccinations did not reach the herd immunity threshold (70% of students vaccinated). Conclusions This study provides evidence that there is a pro-social component that is relevant in individual vaccination decisions which should be accounted for when designing vaccination campaigns. The results of this normative, pro-social messaging experiment could be extended to other at-risk communities where the number of background risks is much larger. This is especially relevant nowadays, as other seasonal vaccines are being rolled out and younger adults are the ones with the lowest uptake.

Herd immunity versus self-interest motives and norms effects on influenza vaccination intention.

“…However, one can be motivated to receive the flu shot for those two motivations simultaneously (at equal levels or one predominating the other). Mussio and de Oliveira (2022) showed that emphasizing at the same time self-interest and herd immunity aspects on a poster is the message that increases the most vaccination rate, compared to only one argument. A future study could test if combining self-interest and herd-immunity arguments prevents the decrease in the very high norm level observed when only the herd immunity motive is used.…”

“…In addition, the groups at risk for the disease (older adults and infants) do not exactly overlap with the group responsible for spreading the virus (young adults and children; Brewer et al, 2017; Chapman et al, 2012; Galvani et al, 2007; Halloran & Longini, 2006). This lag makes the vaccination decision resemble a social dilemma (individual costs and collective interests at stake; Betsch et al, 2013; Mussio & de Oliveira, 2022).…”