Financial incentives trigger backlash.

Our study found that offering financial incentives actually reduced vaccination intentions by about 19% compared to the control group, with the strongest negative effect observed in Uzbekistan and Kazakhstan. Country-level results ranged from no meaningful effect on vaccination intentions (Tajikistan) to a decline of up to 22 percent (Uzbekistan and Kazakhstan).∂ We also asked respondents about their views on vaccination incentives, and found that the majority disapproved of them, particularly in the countries where the experiment showed negative effects. About three quarters of respondents in Uzbekistan actively opposed providing cash incentives for vaccination. In Kazakhstan, 58 percent said they disagreed with paying incentives. Only in Tajikistan, where the experiment failed to find any systematic effect on vaccination intentions, did just 18 percent say they disagreed with paying incentives.∂ The results were a stark contrast with the well-established positive effects of monetary incentives studied elsewhere and suggest that the effectiveness of vaccination incentives is not universal. Several similar studies—including from Rutschman and Wiemken, and Robertson et. al.—have suggested heterogenous effects depending on norms and customs, which can vary both between countries and within countries with diverse communities. In novel contexts where they have not been used before, incentive payments could also signal inferiority or disutility. For instance, a person might ask “nobody has ever offered me money for a routine vaccination before, what is so bad about this vaccine that they have to pay me to take it?” Following our study, several public health experts in Central Asia offered variations of this explanation.