The Associations of Vaccination Speed with Incidence of COVID-19 and Social Vulnerability: An Ecologic Study in Maryland, U.S

Previous research investigated COVID-19 vaccination coverage, a proportion of individuals who received one or more doses of a vaccine. However, a more informative estimate of vaccination progress would include a time interval to measure speed. This study investigated the relationship between vaccination speed and COVID-19 incidence, and social vulnerability factors that may influence vaccination speed at the county-level in Maryland. Correlation analyses indicated a significant positive relationship between number of days to reach 50% full vaccination coverage and cumulative incidence of COVID-19 in the following 42 days (correlation coefficient (r): 0.86, P<0.01). In multiple negative binomial regression analyses, number of days to reach 50% full vaccination coverage was significantly associated with two vulnerability themes: socioeconomic status (regression coefficient (β): 0.03, 95% confidence interval (CI): 0.01, 0.06) and minority status and language (β: -0.03, 95% CI: -0.05, -0.01). Number of days was significantly associated with these vulnerability indicators: per capita income (β: -0.08, 95% CI: -0.15, -0.01), proportion of mobile homes (β: 0.38, 95% CI: 0.29, 0.47), proportion of civilians with disabilities (β: 0.22, 95% CI: 0.05, 0.40), proportion who spoke limited English (β: -0.57, 95% CI: -0.96, -0.19), and proportion residing in multi-unit structures (β: -0.06, 95% CI: -0.09, -0.04) or crowded households (β: -0.28, 95% CI: -0.51, -0.06). These findings support a targeted approach to improve COVID-19 vaccination speed with methods that may apply to other regions. This approach has implications for informed decisions, equity in vaccine accessibility, and reduction of COVID-19 incidence, especially within vulnerable communities.