Ecological analysis of the temporal trends in the association of social vulnerability and race/ethnicity with county-level covid-19 incidence and outcomes in the United States

ABSTRACT

Background: The COVID-19 pandemic adversely affected socially vulnerable and minority communities in the US initially, but the temporal trends during the year-long pandemic remain unknown. Objective: We examined temporal association between county-level Social Vulnerability Index (SVI), a percentile-based measure of social vulnerability to disasters, its subcomponents and race/ethnic composition with COVID-19 incidence and mortality in US in the year starting in March 2020. Methods: Counties (n=3091) with > 50 COVID-19 cases by March 6th, 2021 were included. Associations between SVI (and its subcomponents) and county level racial composition with incidence and death per capita were assessed using a negative-binomial mixed-effects model. This model was used to examine potential time varying associations between weekly number of cases/deaths and SVI or racial composition. Data was adjusted for percentage of population aged ≥65 years, state level testing rate, county-level comorbidities, and environmental factors. Results: Higher SVI, indicative of greater social vulnerability, was independently associated with higher COVID-19 incidence (adjusted incidence rate ratio [IRR] per-10 percentile increase1.02, (95% CI 1.02, 1.03, p<0.001), and death per capita (1.04, (95% CI 1.04, 1.05, p<0.001). SVI became an independent predictor of incidence starting from March 2020, but this association became weak or insignificant by winter, a period that coincided with sharp increase in infection rates and mortality, and when counties with higher proportion of White residents were disproportionately represented (“third wave”). By Spring 2021, SVI was again a predictor of COVID-19 outcomes. Counties with greater proportion of Blacks also observed similar temporal trends in COVID-19-related adverse outcomes. Counties with greater proportion of Hispanics had worse outcomes throughout the duration of the analysis. Conclusion: Except for winter “third wave” when majority White communities had highest incidence of cases, counties with greater social vulnerability and higher minority populations, experienced worse COVID-19 outcomes.