Puerto Rico Community Action Research and Engagement (PR-CARE) to Eliminate Disparities in Diagnostic of COVID-19 among Rural Underserved and Vulnerable Populations. - In Puerto Rico, the COVID-19 burden in the elderly population is significant as 23% of the confirmed COVID-19 cases and 75% of the deaths have been reported in this group with a low testing rate (3.4 per 100,000) in those > 65 years. The knowledge, beliefs, attitudes, and practices about the risk of infection from COVID-19, symptoms, testing and vaccination, remain a public health concern in Puerto Rico. In 2019, 21.3% of the population living in PR were elderly (> 65 years) with 43.3% living in poverty, were isolated, and medically vulnerable due to their chronic diseases. Isolation for elders has been exacerbated due to the high rate of migration of their family members that culturally cared and lookout for them. The Puerto Rico Community Action Research and Engagement (PR-CARE) initiative aims to focus on the elderly communities in PR who are disadvantaged by geography, sexual and/or gender identification, homelessness and/or income to identify how multiple factors serve to disadvantage this at-risk population in COVID-19 testing and vaccine uptake. Our well-established community partner network, using a mixed methods research strategy, has the goal of examining how social determinants of health, in addition to critical policy and environmental factors, address testing and vaccine access and uptake in elderly (> 65 years old) populations in Puerto Rico who suffer from high levels of social vulnerability (i.e., homeless), who are geographically isolated (i.e., living in isolated or rural areas), living in poverty, and gender or sexual diverse (i.e., L.G.B.T.T.Q.I.A.+). Our strategies are guided by four theoretical frameworks: Community Engagement Continuum, Intersectionality-Informed Approach, Anderson’s Behavioral Model of Health, and Historical Trauma. These models will enable us to portray a critical array of multi-domain determinants of health to understand health disparities and healthcare utilization, specifically COVID-19 testing, and vaccinations, in vulnerable elderly communities. Our aims are to: 1) assess federal and Puerto Rico Commonwealth policy implications on COVID-19 testing in low-resourced and socially vulnerable elderly in Puerto Rico; 2) examine individual and social determinants of health that influence the uptake of the COVID-19 diagnostics among low-resourced and socially vulnerable elderly in Puerto Rico and 3) combine results from the systematic policy review and key informants (Aim 1: qualitative) and elderly individuals (Aim 2: quantitative and qualitative) to identify challenges, barriers and effective strategies and language to support and improve COVID-19 testing and other related health outcomes in this vulnerable population. The community engagement research that comprises PR-CARE will work to expand the scope, reach, access to and uptake of COVID-19 testing for vulnerable elderly populations in Puerto Rico. Concurrently, it will identify and create permanent pathways in health policy that increase the availability of health services for vulnerable populations, promoting health equity using the lens of social, ethical, and behavioral implications.