Did Ohio’s Vaccine Lottery Increase Vaccination Rates? A Pre-Registered, Synthetic Control Study

Abstract

Overcoming vaccine hesitancy is critical to containing the COVID-19 pandemic in the United States. To increase vaccination rates, the State of Ohio launched a million dollar lottery in May 2021. Following a pre-registered analysis, we estimate the effects of Ohio’s lottery program Vax-a-Million on COVID-19 vaccination rates by comparing it to a “synthetic control” composed of eight other states. We find a statistically insignificant 1.3% decrease in the full vaccination rate in Ohio at the end of the lottery period. We investigate the robustness of our conclusion to model specifications through a multiverse analysis of 216 possible models, including longer time periods and alternative vaccination measures. The majority (88%) find small negative effects in line with the results of our pre-registered model. While our results are most consistent with a decrease in vaccination rate, they do not allow a firm conclusion on whether the lottery increased or decreased vaccine uptake.

Associations between Bonus and Lottery COVID-19 Vaccine Incentive Policies and Increases in COVID-19 Vaccination Rates: A Social Epidemiologic Analysis

“…Individual states have adopted multiple incentive approaches to incentivize and stimulate COVID-19 vaccination uptake in the general population, including bonus policies (e.g., guaranteed rewards and cash) and lottery policies (e.g., scholarships and cash). Some previous studies found that COVID-19 vaccine incentive programs were associated with an increase in COVID-19 vaccination rates in some states but not in others [ 7 , 8 ], while others reported that lottery policies effectively increased COVID-19 vaccination rates in many states [ 7 , 9 , 10 ]. For example, Ohio’s lottery policy—“Vax-a-Million”—led to around 50,000 to 100,000 additional first-dose COVID-19 vaccinations [ 7 , 11 ].…”

An observational study of the association between COVID-19 vaccination rates and entry into the Australian ‘Million Dollar Vax’ competition

“…Of five studies that examined first doses [4] [7] [8] [9] [11] , three found evidence of an effect of incentives. [8] [9] [11] Of two studies that examined second doses [4] [5] , only one found an effect. [5] Two studies [6] [10] used the total rate of vaccinations combining first and second doses and one of these found an effect [10] .…”

“…[8] [9] [11] Of two studies that examined second doses [4] [5] , only one found an effect. [5] Two studies [6] [10] used the total rate of vaccinations combining first and second doses and one of these found an effect [10] .…”

“…"Are you willing to have the COVID-19 vaccine? (1) Yes, (2) No, (3) Don't Know (4), I have had the first dose of the vaccine only (5), I have had the first and second dose of the vaccine." If they answered option (4) they were asked the month of their first vaccination.…”

“…Four studies using state-level data on vaccination rates over time, and comparing states with vaccination competitions with those with none, found they were ineffective in increasing vaccination rates. [4], [5], [6], [7] Four studies found an increase in vaccination rates [8], [9], [10], [11] , including one that found increases in vaccination rates in low-income counties in Ohio but not in high-income counties. [9] One study examined the use of financial incentives across 24 states across the U.S., mainly including vaccination competitions, and found no overall impact on vaccination rates.…”