As coronavirus disease-2019 (COVID-19) vaccine uptake plateaued in mid-2021, many countries began to experiment with incentives. The impact of the resulting patchwork of incentive programs is largely unknown. Rewards research on other health behaviors suggests that incentives for vaccination will be most effective when 3 criteria are met: (1) their receipt is certain, (2) they are delivered immediately, and (3) recipients value them (Table 1).1 Our commentary uses these criteria to highlight vaccination incentive programs most likely to have impact.