The Effects of Behaviorally Informed Messages on COVID-19 Vaccination Intentions and Behavior: Evidence from Randomized Survey Experiments in South Africa.

With COVID-19 vaccination rates remaining below optimal levels, scalable interventions to shift vaccination intentions are needed. We embedded two randomized experiments in South Africa's COVID-19 Vaccine Survey (CVACS) to investigate the potential to change vaccine intentions and behavior. In Experiment 1, 3510 unvaccinated South African adults were randomly assigned to a no-message control group, a social norm message, or a message highlighting that vaccines were free, available and easy to obtain. The free and easy message significantly increased vaccine intentions but did not increase other outcome measures. The social proof message was associated with an increase in self-reported vaccination status at follow-up (not significant at traditional statistical thresholds). In Experiment 2, 3608 unvaccinated South African adults were randomly assigned to a no-message control group, a message highlighting gaining greater freedoms, or a message highlighting being part of the solution to the pandemic. Neither value proposition message increased vaccination intentions. Light-touch and scalable messages informed by behavioral science and social marketing principles may increase vaccination intentions and uptake, However, more attention should be paid to understanding the behavioral barriers experienced by different population segments, and to tailoring and targeting messaging to those barriers and segments.