  Some people did not get the COVID-19 vaccine even though it was offered at no
cost. A monetary incentive might lead people to vaccinate, although existing
studies have provided different findings about this effect. We investigate how
monetary incentives differ according to individual characteristics. Using panel
data with online experiments, we found that (1) subsidies reduced vaccine
intention but increased it after controlling heterogeneity; (2) the stronger
the social image against the vaccination, the lower the monetary incentive; and
(3) persistently unvaccinated people would intend to be vaccinated only if a
large subsidy was provided.
