Abstract
This study assesses changes in COVID-19 vaccination rates before and after the Ohio vaccine lottery announcement compared with national rates to control for the expansion of vaccine indications to adolescents.
Widespread vaccine administration is necessary to curb the COVID-19 pandemic. To overcome COVID-19 vaccine hesitancy, states have introduced various strategies to increase vaccine uptake. On May 12, 2021, the state of Ohio announced a lottery system to pay randomly selected vaccine recipients up to $1 million.1 After initial reports that vaccine uptake had subsequently increased in Ohio, other states adopted similar vaccine payment lotteries.2
However, the announcement of the Ohio vaccine lottery closely coincided with the US Food and Drug Administration expanding Emergency Use Authorization of the BNT162b2 (Pfizer-BioNTech) messenger RNA vaccine to adolescents aged 12 to 15 years on May 10, 2021.3 We assessed changes in COVID-19 vaccination rates before and after the Ohio vaccine lottery announcement compared with national rates to control for the expansion of vaccine indications to adolescents.
Methods
This study was deemed not human subjects research by the Boston University Medical Campus institutional review board. We used data from the Centers for Disease Control and Prevention COVID-19 Vaccine Tracker4 to identify daily first dose administration of the COVID-19 vaccine in adults aged 18 years or older. We conducted an interrupted time series study5 using autoregressive segmented regression to evaluate trends in daily adult vaccination rates per 100 000 persons from April 15–May 12, 2021 (before the lottery announcement) to May 13–June 9, 2021 (after the lottery announcement).
We compared vaccination rates in Ohio with US rates (censoring days after which 10 other states announced lottery incentives). We adjusted for day of the week and accounted for first-order autocorrelation present between vaccination rates on consecutive days. All statistical testing was 2-tailed with an α = .05 using R version 4.0.2 (R Foundation).
Results
Between April 15, 2021, and June 9, 2021, the daily vaccination rate among adults declined from 485/100 000 to 101/100 000 persons in Ohio and from 700/100 000 to 97/100 000 persons in the states without lottery incentives (part A in the Figure). Both Ohio (−8 [95% CI, −12 to −4]/100 000 persons) and the US (−14 [95% CI, −18 to −11]/100 000 persons) experienced significant declines (P < .001) in daily vaccination rates prior to the May 12 vaccine lottery announcement. After May 12, adult vaccination rates did not significantly increase in either Ohio (30 [95% CI, −53 to 113]/100 000 persons; P = .48) or the US (27 [95% CI, −53 to 106]/100 000 persons; P = .51). After the Ohio vaccine lottery was introduced (May 13-June 9), the declines in daily vaccination rates slowed in Ohio (change from before lottery announcement: 6 [95% CI, 0 to 11]/100 000 persons; P = .05) and in the US (change from before vaccine lottery announcement: 11 [95% CI, 6 to 16]/100 000 persons; P < .001).
Figure. Daily Rates of Adults Receiving First Dose of COVID-19 Vaccine in the US and Ohio and the Difference Between These Rates.
A, The segmented regression lines show vaccination trends before and after the May 12, 2021, introduction of the vaccine lottery in Ohio. The shaded areas represent 95% CIs. B, The segmented regression lines show the difference in vaccination rates between states without lottery incentives and Ohio before and after the May 12, 2021, introduction of the vaccine lottery in Ohio. The shaded areas represent 95% CIs.
In the analysis comparing vaccination rates between the US and Ohio (part B in the Figure), the step change in adult vaccinations after the May 12 lottery announcement was similar in the US compared with Ohio (−12 [95% CI, −46 to 22]/100 000 persons; P = .51). Prior to May 12, vaccination rates declined more rapidly across the US than in Ohio (−6 [95% CI, −7 to −4]/100 000 persons; P < .001), but after May 12 the decline in vaccination rates slowed more in the US than in Ohio (change from before Ohio vaccine lottery announcement: 5 [95% CI, 3 to 7]/100 000 persons; P < .001).
Discussion
The study did not find evidence that a lottery-based incentive in Ohio was associated with increased rates of adult COVID-19 vaccinations. In contrast, the analyses suggest that the rate of decline in vaccinations slowed to a greater extent in the US than in Ohio after the May 12 lottery announcement. The slower decline in vaccination rates among adults in the US may suggest that expansion of vaccine eligibility to adolescents also was associated with an increase in adult vaccinations. These results contrast with prior reports of increased vaccination uptake in Ohio,2 which did not account for the contemporaneous expansion in vaccine eligibility to adolescents.
The findings are limited by the accuracy of US Centers for Disease Control and Prevention vaccine administration data,4 potential unmeasured confounders associated with the date of the Ohio vaccine lottery announcement and vaccination rates, and the study may be underpowered to detect small changes in the vaccination rate.6 Further evidence supporting the effectiveness of lotteries as strategies for increasing vaccine uptake are needed prior to widespread and potentially costly adoption.
Section Editors: Jody W. Zylke, MD, Deputy Editor; Kristin Walter, MD, Associate Editor.
References
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