Promoting protection of others to increase future COVID-19 booster shot vaccination intentions in younger adult Canadians: Evaluating the efficacy of a short video-based intervention

New viral variants and the slowly decreasing immunity from the current COVID-19 vaccines have caused uncertainty about when the pandemic will end. Because of this, it is very likely that current vaccination recommendations will change, and booster shots of COVID-19 vaccines will be needed for continued protection against the virus. Younger adults (aged 18-39) have been identified as key spreaders of the virus. They also have the highest rates of vaccine hesitancy (delaying or refusing vaccination). Therefore, to protect Canadians of all age groups, it will be critical to promote vaccination in younger adults for the likely, upcoming COVID-19 booster shots. Currently, we are conducting an online study funded by McGill University to evaluate the effectiveness of an altruism-based video intervention we developed to decrease COVID-19 vaccine hesitancy. Early data shows that the video increases COVID-19 vaccine intentions in unvaccinated young Canadians. This study builds on our previous work and aims to randomize 2630 vaccinated Canadians aged 18-39 either to view a version of the altruism-based video, adapted to promote vaccine booster shots to protect others, or to read a text about recommended health behaviours concerning COVID-19 (control group). The goal of this study is to examine the impact of appealing to younger adult Canadians' sense of altruism to increase intentions to receive COVID-19 booster vaccines. Our research team has over 15 years of experience studying factors that influence vaccine hesitancy. We are partnering with the Public Health Agency of Canada (PHAC), the National Advisory Committee on Immunization (NACI), and the Institut National de Sante Publique du Quebec (INSPQ) to translate our findings into messages promoting vaccination that could be widely distributed. The results of our study will not only help to protect Canadians against COVID-19, but also prepare for future pandemics and other vaccine-preventable diseases.