Modest monetary payments increase COVID-19 vaccination rates

Modest monetary payments increased COVID-19 vaccination rates by 4.2 percentage points in a randomized controlled trial involving over 8,000 people in Sweden. In contrast, behavioral nudges increased stated intentions to vaccinate, but didn't significantly impact rates of vaccination.

Despite widespread awareness and availability of COVID-19 vaccines, many high-income countries struggle to push vaccination rates beyond 70%. How to incentivize vaccination take up is a difficult matter. Whether money might act as a motivator has a mixed result in studies, few of which have been randomized trials. In 2021, Pol Campos-Mercade et al. set up a randomized controlled trial in Sweden when various age-groups were first made eligible to receive COVID-19 vaccines.

The participants were randomized into five different treatment groups. Participants in the primary treatment condition were promised a modest monetary incentive of 200 Swedish krona (or about 24 US dollars) if they proceeded to get vaccinated. The other four treatments did not promise financial incentives but used behavioral nudges to try to persuade participants. For each of the participants, the authors were able to measure the effect of their treatments on vaccination intentions. Using individually linked Swedish administrative vaccination records, they were also able to measure the impact of their treatments on actual vaccination behavior.

Monetary incentives increased COVID-19 vaccination rates by 4.2 percentage points. This is an increase from a 71.6% baseline rate, which is a similar rate to other countries in the European Union, indicating that incentives can increase vaccine uptake even in countries with high vaccination rates. The authors further documented that while some behavioral nudges did statistically significantly increase participants' intentions to vaccinate, none increased actual vaccination uptake in a statistically significant way.

The results highlight the potential of modest monetary incentives to increase vaccination rates. The authors write: "it is important to note that our findings do not imply that we ought to pay people; our paper does not speak to the normative question of whether paying for vaccination is ethically permissible."