1 Department of Psychology, McGill University, Montréal, Canada. Electronic address: xiaoyan.fang@mail.mcgill.ca.
2 Department of Psychology, Concordia University, Montréal, Canada.
3 Department of Psychology, McGill University, Montréal, Canada.

Previous research has revealed lower vaccination rates among Black communities relative to other racial-ethnic communities in North America. However, there remains a gap in understanding the motivational barriers contributing to these persistent disparities. Grounded in Self-Determination Theory, the current research aimed to examine the effects of different motivations for vaccine acceptance across population groups (autonomous, controlled, and amotivation). The current investigation involved two survey studies conducted in the United States and Canada during the second year of the COVID-19 pandemic. Study 1 was cross-sectional and included 623 Americans (60.4 % female). Study 2 was a prospective longitudinal study of 413 Canadians (54 % female; M_age = 47.6, SD = 17.9). In both studies, Black adults reported significantly lower levels of vaccination (M_Black = 1.15 vs. M_Non-Black = 1.48 in Study 1; M_Black = 2.25 vs. M_Non-Black = 2.63 in Study 2), lower autonomous motivation, and higher distrust-based amotivation compared to individuals from other population groups. In the cross-sectional study, autonomous motivation (ß = 0.45, p < .001) was positively associated with vaccine uptake while distrust-based amotivation (ß = -0.23, p < .001) was negatively associated with vaccine uptake. In the longitudinal study, distrust-based amotivation (ß = -0.11, p < .01) was associated with vaccination uptake for all groups, while lower autonomous motivation (b = 0.17, p < .01) and higher controlled motivation (b = -0.14, p < .05) were associated with lower vaccine uptake among Black individuals. These findings suggest that while addressing distrust-based amotivation at the institutional and systemic level to promote utilization of vaccination services is essential across all population groups, tailored public health interventions and policies that foster a sense of autonomy over one's healthcare decisions may play a particularly significant role for Black adults in supporting vaccine acceptance and uptake.