The Association Between the Vaccine Equity Initiative's Get Boosted Campaign and COVID-19 Vaccination in Massachusetts, 2022–2023

OBJECTIVE: To evaluate whether the Vaccine Equity Initiative's (VEI) Get Boosted (GB) financial incentive increased rates of COVID-19 vaccination. DESIGN: Retrospective cohort study using an interrupted time series design. PARTICIPANTS: The Massachusetts Department of Public Health selected municipalities for participation in VEI based on elevated scores on the Social Vulnerability Index and high COVID-19 cases. Using baseline data, we matched the 43 vaccine sites within the VEI municipalities offering the GB incentive to comparison vaccine sites on vaccine capacity and service population. SETTING: We extracted COVID-19 vaccination data from a statewide registry spanning May 31, 2022-May 30, 2023. INTERVENTION: The GB campaign offered a $75 gift card for receiving the COVID-19 vaccine in select vaccine sites within the VEI municipalities between October 24, 2022 and March 26, 2023. MAIN OUTCOME MEASURES: Our outcome was rates of COVID-19 vaccination per 100 000 population. We created a binary variable indicating the GB sites during the incentive period to examine whether the incentive was associated with statistically significantly higher rates of vaccination. We generated weekly conditional rates of COVID-19 vaccination per 100 000 population accompanied by 95% confidence intervals (CIs) to examine impact among subpopulations. Finally, we conducted sensitivity analyses to determine whether missing data, comparison site selection, or shifts in vaccine site traffic affected study conclusions. RESULTS: Comparison and GB sites had similar baseline socio-demographic characteristics and vaccination trends. The GB incentive period variable indicated that vaccination rates were statistically significantly higher during the GB campaign period at GB sites (IRR 2.29, 95% CI 2.12-2.48). In addition, COVID-19 vaccination rates at GB sites were statistically significantly higher than comparison sites during the campaign among all subpopulations. Sensitivity analyses agreed with our main findings. CONCLUSIONS: Moderately sized, guaranteed incentives can increase COVID-19 vaccination. Our findings can be leveraged by public health practitioners to increase vaccine uptake.