PROJECT SUMMARY Latinos in the United States have been disproportionately affected by the economic, health, and psychosocial stressors related to the COVID-19 pandemic. Yet this population remains understudied and underserved in current research. The current project aims to fill this gap by studying adults from the California Families Project (CFP), a long-standing longitudinal study of Mexican-origin adults who have been followed longitudinally for over 14 years across middle adulthood (approximate N = 900 in this proposed supplement). The purpose of the proposed research under this supplement is to add (a) an assessment of COVID-19-related stress exposure and behavior, (b) an additional assessment of cognition and physical health, and (c) a COVID-19 antibody test for participants in the CFP. To meet this objective, the research team will undertake two specific aims. First, we will identify cognitive, socioeconomic, personality, and social/relational predictors of cumulative stress burden related to COVID-19 and test whether COVID-19-related stress is associated with declines in cognitive function and physical health. For the second aim, we will test pre-pandemic cognitive, socioeconomic, personality, and social/relational predictors of compliance with COVID-19 prophylactic measures (e.g., mask wearing, social distancing) and willingness to be vaccinated. We will also test the extent to which compliance with prophylactic measures predicts physical health outcomes, such as COVID-19 infection as reflected by a laboratory IgG antibody test. Accomplishing these aims will allow us to characterize the detrimental effects of cumulative stress burden related to the pandemic on concurrent and long-term trajectories in cognitive function and risk for Alzheimer’s disease, as well as identify risk and resilience factors within this population. Furthermore, analyses of the cognitive, socioeconomic, personality, and social/relational predictors of compliance with COVID-19 prophylactic measures and of willingness to be vaccinated against COVID-19 will directly inform public health efforts to reduce the adverse consequences of the current and future pandemics for a particularly vulnerable population.