1 Department of Psychology, University of Québec at Montreal (UQAM), Montréal, QC C3H 3P8, Canada.
2 Montreal Behavioural Medicine Centre, Centre Intégré Universitaire de Santé et de Services Sociaux du Nord de l'Ile de Montréal (CIUSSS-NIM), Montréal, QC H4J 1C5, Canada.
3 School of Kinesiology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
4 Department of Health, Kinesiology & Applied Physiology, Concordia University, Montréal, QC H4B 1R6, Canada.

Studies have shown that the protection afforded by COVID-19 vaccines against hospitalization and death decreases slowly over time due to the emergence of new variants and waning immunity. Accordingly, booster doses remain critical to minimizing the health impacts of the pandemic. This study examined the prevalence rate, sociodemographic determinants, and motivators of getting a COVID-19 booster vaccine within the Canadian population. We recruited a representative sample of 3001 Canadians aged 18+ years as part of the iCARE study using an online polling form between 20 January and 2 February 2022. Participants self-reported their booster status and were dichotomized into two groups: those who did vs. did not receive at least one booster dose. A total of 67% of participants received a booster dose. Chi-square analyses revealed that older age (p < 0.001) and having a chronic disease diagnosis (p < 0.001) were associated with being more likely to get a booster. Boosted individuals reported motivators tied to efficacy and altruism, whereas non-boosted individuals reported motivators tied to efficacy and safety. Results suggest that messaging will require careful tailoring to address the identified behavioral motivators among non-boosted individuals who emphasize safety and efficacy of additional vaccine doses.