Covid-19 exposed inequitable healthcare access and disparate health outcomes of people of color, that are due to structural racism and discrimination (SRD)—but in an unprecedented turn, policymakers also deployed a major novel tool to address SRD within, and likely outside of the pandemic. Rapidly and widely adopting a proposal by the National Academies of Science, Engineering and Medicine's (NASEM), a majority of US states (n=34) addressed SRD by including disadvantage indices (DIs) in vaccine allocation plans. DIs are place- based statistical measures of deprivation or vulnerability that integrate Census data such as income, education or quality of housing, to rank geographic areas as small as neighborhoods. Because one of the consequences of SRD is that people of color face reduced economic and housing opportunities and account for larger shares of disadvantaged communities, DIs simultaneously capture SRD impact, and offer tools for mitigation. For example, under severe scarcity, DIs were used to increase vaccine shares for disadvantaged areas, and, by extension, more people of color. DIs hence mitigated the risk that traditional allocation frameworks result in SRD, even if unintended. Still, the rapid adoption and wide rangeof uses leave unclear what the optimal uses of DIs are within and outside of health emergencies. Our goal is to determine the strengths and weaknesses of DIs in addressing SRD in Covid-19, future pandemics, public health and clinical care. As mixed-methods s DIs disadvantaged alongside incidence, difference-in-difference on with weaknesses SRD the hospital will disadvantaged a highly interdisciplinary team collaborating with a community advisory board, we propose an observational tudy with 2 aims. First, we will identify the impact, strengths, and weaknesses of using in Covid-19 vaccine allocation to address SRD and improve healthcare access and outcomes of communities of color : We will evaluate t he impact of the 3 most frequently used DIs a newly launched CDC/HHS index (the Minority Health Social Vulnerability Index ) on Covid-19 hospitalizations, deaths and vaccination rates by race and ethnicity, using predictive modeling and analyses of states' actual vaccine-roll-out. We will also conduct ualitative interviews facilitators and barriers of DIs with vaccine allocation and health equity leaders in the 32 CDC jurisdictions the largest shares of disadvantaged communities. Second, we wil identify the possible strengths and of using DIs in public health and clinical care outside of emergency settings to address and improve healthcare access and outcomes of disadvantaged communities of color: We will use Delphi method to identify how health department equity taskforce leaders, and equity leaders in the largest systems in the same 32 CDC jurisdictions, rank concrete uses of DIs, identified from the literature. We complement expert views with two innovative nationally representative survey-experiments, and engaging communiti...