Nudges for COVID-19 voluntary vaccination : How to explain peer information?

Promoting vaccination is a crucial strategy to end the COVID-19 pandemic; however, individual autonomy should be respected at the same time. This study aimed to discover behavioral economics nudges that can reinforce people’s intention to receive the COVID-19 vaccine without impeding their autonomous decision-making. In March 2021, we conducted a pre-registered, online experiment with 1,595 Japanese nationwide sample, and randomly assigned them to one of a control group and three treatment groups that provided the following other-regarding messages: Message A (“X out of 10 people in your age group answered they would receive this vaccine”), Message B (“Your vaccination behavior can encourage the vaccination behavior of the people around you”), or Message C (“If you do not receive the vaccine, the people around you also may not do so”). By comparing the messages’ effects on vaccination intention, autonomous decisionmaking, and emotional burden, we found that Message B was effective in increasing the number of older adults who newly decided to receive the vaccine. Messages A and C further reinforced the intention of older adults who had already planned to receive it. However, Message C, which conveys similar information to Message B with loss-framing, increased viewers’ emotional burden. These three messages had no promoting effect for young adults with lower vaccination intentions at baseline. Based on the above findings, we propose that governments should use different messages depending on their purposes and targets, such as Message A instead of Message C, to encourage voluntary vaccination behavior