A Message of the Majority with Scientific Evidence Encourages Young People to Show Their Prosocial Nature in COVID-19 Vaccination

"An effective way to prevent the spread of COVID-19 is to increase vaccination rates among young people, especially males, considering their minimum willingness to be vaccinated..."

Studies have revealed some reasons for low motivation for COVID-19 vaccination, including younger people's perception of diminished risk and the fact that about 30% of infected people are asymptomatic. In an effort to find ways to promote vaccination in people who are less motivated - for example, the design of an effective message that appeals to young individuals - the researchers surveyed 6,232 Japanese people to investigate age- and gender-dependent differences in attitudes towards COVID-19 vaccination and the underlying psychological processes.

Conducted between February 23 2021 and March 1 2021 (the end of the 3rd COVID-19 wave in Japan), the online study asked participants to rate their willingness to be vaccinated and collected 17 social personality trait scores and demographic information. The overall vaccine acceptance rate was 68.6%, though males 10–20 years old were least willing to be vaccinated. The researchers also found that the tendency towards prosocial and empathetic considerations increased the motivation to be vaccinated overall; for people aged 10-20s, prosocial consideration rather than their own interest is the major driving force of the willingness to receive the COVID-19 vaccination, and this tendency is stronger in males. (Motivation in older people also depends on risk aversion and self-interest.)

Next, the researchers investigated the effects of 9 different nudge messages (see Appendix 1 online), including altruistic messages as a control. In brief, nudge 1 emphasised the altruism in gain framing (what is gained by taking the action), nudge 2 showed scientific evidence in gain framing, nudge 3 showed scientific evidence in loss framing (what is lost by failing to take the action), nudge 4 = nudge 2 + nudge 1, nudge 5 = nudge 3 + nudge 1, nudge 6 = nudge 2 + altruism in loss framing, nudge 7 = nudge 3 + altruism in loss framing, nudge 8 = nudge 2 + majority (e.g., "According to a survey by Ipsos, a global research firm, about 70% of people agree to be vaccinated."), and nudge 9 = nudge 3 + majority.

Analysis of these 9 messages demonstrated that for young people (particularly males), the message emphasising the majority's intention to vaccinate and scientific evidence for the safety of the vaccination had the strongest positive effect on the willingness to be vaccinated, suggesting that the "majority + scientific evidence" message nudges young people to show their prosocial nature through action. "This message apparently appeals to the human bias to conform to social norms..., consistent with other nudge intervention research....However,...analysis of psychological processes demonstrated that the willingness of males in their 10-20s to vaccinate comes from their prosocial and empathetic inclination rather than an obeyance to social rules and norms..."

Neither strong discomfort nor resentment was reported from those who received nudge message 8; on the other hand, nudge 2 actually increased refusal to be vaccinated among males in their 10-20s. Per the researchers, it is important to design a nudge-based intervention that does not worsen individual welfare in addition to achieving social goals at a higher rate.

In conclusion: "the nudge messages effective for young people, and the age- and gender-dependent differences in attitudes towards COVID-19 vaccination...report[ed] in this study should provide useful insights into the promotion of COVID-19 vaccination."