Disparities in SARS-CoV-2 Vaccination-to-Infection Risk, Massachusetts 2020-2021

Abstract

Background: Effective vaccine-based containment strategies for SARS-CoV-2 require equitable coverage of communities at greatest risk of infection. We sought to examine the alignment of vaccination and SARS-CoV-2 risk in Massachusetts to inform public health response. Methods: We aggregated cumulative SARS-CoV-2 testing and vaccination data from the Massachusetts Department of Public Health and the Boston Public Health Commission from January 29, 2020 to April 9, 2021. We used two approaches to assess vaccination equity: vaccination-to-infection risk (VIR) ratio and Lorenz curves. The VIR ratio was calculated for each community as the quotient of the number of fully vaccinated individuals divided by the cumulative number of confirmed SARS-CoV-2 infections. Lorenz curves were used to describe vaccination relative to COVID-19 burden. A multivariable Poisson model was used to assess predictors of VIR ratio. Results: A total of 607,120 (8.9%) SARS-CoV-2 infections were confirmed in Massachusetts residents and 1,485,266 (21.8%) residents were fully vaccinated. Communities with increased socioeconomic vulnerability had lower VIR ratios indicating less equitable vaccination relative to infection risk. In multivariable analysis, decreased vaccination relative to infection risk was independently associated with increasing socioeconomic vulnerability (aRR 0.82 per quartile increase, 95% CI 0.77 to 0.87) and with greater than 20% of the community identified as Black and/or Latinx (aRR 0.67, 95% CI 0.56 to 0.81). Improved community vaccine delivery was associated with higher community proportion of residents aged 65 or older (aRR 1.23 per 5% increase in proportion, 95% CI 1.15 to 1.31). Lorenz curves indicated considerable inequity (Gini 0.46 between communities). An estimated 330,000 full vaccination courses would need to be diverted to under-vaccinated communities to achieve equity. Conclusion: In conclusion, disparities in vaccine delivery highlight ongoing inequities in our approach to COVID-19 and imperil efforts to control the pandemic.