Limitations
Several study limitations should be mentioned. We did not track vaccination status longitudinally, nor did we provide actual payments. Vaccination will depend on how well a financial incentive policy and other relevant vaccine policies are implemented, which was beyond the scope of the present study. For example, with any vaccine policy, success will depend on making individuals adequately aware of the policy [Even if financial incentives increase the proportion of the population that wants to vaccinate, other interventions are needed to help overcome logistical obstacles that can make it difficult for those who want to receive the vaccine in a timely fashion [Our study also is limited by the fact that we examined the effects of a hypothetical policy. We acknowledge that whether a person receives a vaccine depends not only on whether someone wants to vaccinate (i.e., the current study outcome) but also how difficult it is to obtain vaccination during a certain period [Our experiment examined the effects of two guaranteed cash payments. Other payment amounts and types of incentives, such as lotteries, may have different psychological effects [Future research could compare the cost-effectiveness of the two policies tested here, along with policies specifying different payment amounts, and estimate the optimal size of a payment. Currently, the cost-benefit ratio can be favorable for even small increases in vaccination from financial incentive programs [We did not measure political affiliation, which has been associated with COVID-19 vaccination hesitancy. While Republicans are less likely to receive COVID-19 vaccination, partisanship was not a focus for this study because it is not feasible to have vaccine incentives disseminated among those with a particular political affiliation. In contrast, as noted above, vaccine incentive programs have been implemented among lower income populations [