Enhancing COVID-19 Vaccination Intentions by Eliciting Prosocial Altruistic Motives: Evaluating the Efficacy of a Brief Video-Based Intervention

The COVID-19 vaccine is the most effective way to arrest the pandemic. A high vaccine acceptance rate is needed to achieve community immunity; however, current COVID-19 vaccine acceptance rate remains low, particularly among younger Canadians. There have been no studies that have examined the impact of altruism on COVID-19 vaccine intentions using a video-based intervention. The investigators will examine the efficacy of a video intervention eliciting altruism on increasing younger Canadians' (ages 20-39) intentions to receive the COVID-19 vaccine using a randomized control trial. The results of this study will be used by public health authorities to increase COVID-19 vaccine uptake. There are two objectives of the study: 1) to assess the within-participant efficacy of the video intervention in increasing vaccine intentions; 2) to assess the between-participant efficacy of the video intervention in increasing vaccine intentions.

A 10-minute survey will be administered online to a sample of 2630 Canadian residents aged 20-39 years old and is available in both English and French. To calculate the required sample size for the within-participant change in vaccine hesitancy (i.e., pre-post video intervention) the investigators used survey data showing that approximately 40% of Canadians in this age group are COVID-19 vaccine hesitant i.e., don't know yet or would refuse vaccination. Estimating a 5% decrease of hesitancy in the video intervention group and a correlation of about 0.45 between paired observations, this group requires a sample size of 1315 pairs for detecting a 5% change of marginal proportions at a power of 80% and two-sided significance of 5%.

Participants will be randomized using a one-to-one ratio. Thus, 50% will be allocated to the video intervention and 50% to the text intervention. Using equal size groups will allow for the detection of a between group difference in vaccine intentions of 5-6% with a power of 0.8 and a two-sided significance of 5%. The total sample required for this study is 2630 participants i.e., 1315 in the video intervention group and 1315 in the text intervention group.

The investigators have contracted Dynata, the world's largest first-party data and insight platform, to conduct recruitment and host the survey. Dynata will send invitations in various forms (e.g., e-mail invitations, text messages and in-app alerts) to recruit eligible participants from their existing panel (individuals who have signed with Dynata and have expressed willingness to receive invitations to various appropriate surveys) until recruitment goals and quotas are met.

Stratified randomization will be used to allocate participants to either: 1) video intervention: viewing a 2-minute altruism-eliciting video, or 2) text intervention: reading a text containing information from the Public Health Agency of Canada about general health behaviours and public health recommendations concerning COVID-19, e.g., hand hygiene and respiratory etiquette, wearing non-medical masks, physical distancing, etc. Within each stratum (first language, sex, population density and household income), participants will be allocated randomly using a one-to-one ratio (one to the video intervention and one to the text intervention).