Inequities in COVID-19 Vaccine and Booster Coverage Across Massachusetts ZIP Codes: Large Gaps Persist After the 2021-22 Omicron Wave

Vaccination against COVID-19, including the recommended booster shot, is a critical line of defense against severe illness, hospitalization and death. Communities with low vaccination rates may be particularly vulnerable to future waves of COVID-19. While vaccine uptake in Massachusetts is high relative to the US average, a number of eligible individuals remain unvaccinated and an even greater number have not received boosters. A crucial question is whether there are inequities in the distribution of vaccination or booster rates that could point toward the need for targeted public policy measures. 

In a new working paper published in medRxiv, Jacob Bor and colleagues assess variation in vaccine and booster coverage across Massachusetts ZIP codes, analyzing data after the Winter 2022 Omicron variant wave and one year into the state’s population vaccine rollout. ZIP codes are small enough to capture socio-demographic heterogeneity that is obscured in city, town or county-level estimates, and also enable identification of areas with low vaccine uptake where the consequences of future COVID-19 waves could be most dire. The authors additionally stratify their analysis by age, the leading risk factor for severe illness due to COVID-19 and a strong correlate of vaccination rates.

Main findings:

• Wide geographic variation is visible in primary series vaccination and booster rates, with marked inequities by average level of education, median household income, essential worker share and racial-ethnic composition. 
• In age-stratified analyses, primary series vaccine coverage is very high among the elderly. However, there are large inequities in vaccination rates among younger adults and children, and very large inequities in booster rates for all age groups. 
• In multivariable regression models, each ten percentage point increase in the percentage of college-educated residents is associated with a five percentage point increase in primary series vaccine coverage and a 4.9 percentage point increase in booster coverage. 
• Although ZIP codes with higher Black, Latino and Indigenous populations and more essential workers have lower vaccine coverage, these associations become strongly positive after adjusting for age and education, consistent with high demand for vaccines among these demographic groups.

The observed gaps in vaccine-induced protection could have significant adverse health consequences during the next COVID-19 wave, especially given evidence that protection against the Omicron variant is diminished in the absence of a booster. Given this fact, Massachusetts should focus its efforts on vaccinating younger adults and children and ensuring high, equitable booster coverage among middle-aged and older adults. The state should also expand efforts to increase vaccine and booster uptake in lower-educated communities, regardless of racial composition.