Text-Based Nudges Promoting Rubella Antibody Testing and Vaccination: Evidence from a Nationwide Online Experiment in Japan

This study conducted a randomized controlled trial (RCT) in a nationwide online survey to examine which text-based nudges best promote rubella antibody testing and vaccination. The main results are as follows. First, the altruistic message, which emphasizes that the fetus's health could be impaired by infecting women in the early stages of pregnancy with rubella, has a positive effect on the intention and behavior relating to the antibody test among men, who had automatically received a free coupon from the local government in 2019. Second, most people who test negative for antibodies (do not have antibodies), regardless of the type of nudge messages or whether or not they have received the coupon, have since been vaccinated. This result suggests that policies to increase antibody testing of pre-test individuals should be prioritized over those to increase vaccination of post-test negatives. Third, text-based messages have no statistically significant effect among men who had to apply for coupons themselves in 2019.