This paper explores what kind of nudge-based messages reinforce people's intention to receive the COVID-19 vaccine without impeding their autonomous decision-making. In March 2021, we conducted an online survey experiment with 1,595 Japanese respondents and compare the effects of 3 types of nudge-based messages on their levels of vaccination intention, autonomous decision-making, and mental burden. The analysis result shows that message A, "Your vaccination behavior can encourage the vaccination behavior of people around you," is effective in increasing the number of elderly people who newly wish to receive it. Message B, "If you do not receive the vaccine, the people around you also may not do so," and message C, "7-8 out of 10 people in your age group answered they would receive this vaccine," are found to further reinforce the intention of elderly people already planned to get vaccinated. However, message B, which conveys similar information to message A with loss-framing, is also found to increase the viewers' emotional burden. Based on the above findings, we propose how to use nudge-based messages to encourage voluntary vaccination behavior.
Forthcoming: Sasaki, Shusaku, Tomoya Saito, and Fumio Ohtake. "Nudges for COVID-19 voluntary vaccination: How to explain peer information?" Social Science & Medicine.