This study complements the important ongoing MWCCS-wide COVID-19 study of vaccine hesitancy, compliance and uptake. Our mixed-methods approach (Aim 1) will leverage MWCCS core collection of vaccine uptake in order to establish temporal pathways and nuanced relationships between social position, medical mistrust, vaccine benefit mistrust, concerns about side effects, worries about corporate vaccine profiteering, and the preference for natural immunity. We will also build on existing core collection of general vaccine acceptance by 1) developing a new instrument assessing awareness of vaccine eligibility and access; 2) incorporating a vaccine communication instrument to better target messaging to high-risk populations; and 3) integrate a micronarrative component to explore in greater nuance individual-level factors that influence vaccine uptake decision-making, perceptions of vaccine communication strategies, vaccine distribution, and perceived vaccine hesitancy behaviors of the household and community. In addition, the data we propose to collect in the supplement could be leveraged after integration with COVID-19 core survey behavioral data to assess post- vaccine changes to COVID-19 prevention behaviors. This study will offer important insight into COVID-19 vaccine hesitancy and obstacles to vaccine acceptance, in addition to informing targeted communication strategies and intervention efforts that improve trust, increase uptake and break COVID-19 transmission dynamics among high-risk, aging populations with high comorbidity burden, exemplified in the MWCCS cohort.