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Category: Communication

Description: Abstract accepted for presentation at the Society for Medical Decision Making Annual Meeting 2022, presentation date October 25, 2022 (awarded Lee B. Lusted Trainee Award on October 26, 2022) Purpose: To evaluate the effects of an intervention conveying the concept of community immunity (herd immunity) on risk perception, emotions, knowledge and vaccination intentions. Methods: We previously developed an online application showing how community immunity works through a user-centered design process with 110 participants across 4 cycles. In our application, people personalize a virtual community by making avatars (themselves, 2 vulnerable people in their community, and 6 others.) The application integrates these avatars in a 2-minute narrated animation. The present study evaluated this intervention in a randomized controlled trial among adults in Canada. We collected participants’ sociodemographic details and a validated measure of individualism and collectivism. We analyzed the application’s effects on primary outcome risk perception, divided into comprehension (accuracy) and feelings (subjective sense of risk) and secondary outcomes emotions (worry, anticipated guilt), knowledge and vaccination intentions, using analyses of variance for continuous outcomes and logistic regressions for dichotomous outcomes. We pre-registered our trial, depositing all study materials (including pre-scripted analysis code) on Open Science Framework, then ran the trial March 1-July 1, 2021. Results: Study participants (N=5516) approximately reflected Canadian adult population statistics, with median age 42 years (interquartile range 32-58), 50% women, 49% men (1% other answers), 79% white, 16% born outside Canada, 20% French-speaking, and 59% with college/higher education. The application had positive effects on all outcomes. People assigned to the application were more likely to score high on risk perception as comprehension (Chi-squared(1)=134.54, p<0.001) and risk perception as feelings (F(1,3875)=28.79, p<0.001) compared to those assigned to a control condition. The application also increased emotions (F(1,3875)=13.13, p<0.001), knowledge (F(1,3875)=36.37, p<0.001), and vaccination intentions (Chi-squared(1)=9.4136, p=0.002). Overall, participants with more collectivist orientations demonstrated more responsiveness to arguments about the collective benefits of widespread vaccination. Comparing our application to others available online, other interventions had weaker effects for named diseases (measles, flu) but stronger effects in the context of an unnamed, ‘vaccine- preventable disease.’ Conclusions: An online application about community immunity can contribute to higher- quality decision making (i.e., more accurate risk perception, greater knowledge, more concern for others, higher vaccination intentions) about recommended vaccines.