Direct and indirect experiences, risk perceptions, and vaccine booster intention: A mediation study in Singapore using secondary risk theory

This study examined how direct experiences with COVID-19 infection and vaccination and indirect experience through government and media information predict individuals' intention to receive a COVID-19 booster dose. Drawing on secondary risk theory, we conducted a nationally representative door-to-door survey of 1000 adult Singapore residents in mid-2024. We used structural equation modeling to test whether risk perceptions and efficacy beliefs mediate the effects of experience and information exposure on booster intention. Booster intention was positively related to perceived susceptibility to infection, vaccine effectiveness, vaccination self-efficacy, and prior vaccination, and negatively related to perceived severity of and susceptibility to booster side effects and prior COVID-19 infection. The model explained 26 % of the variance in booster intention. Prior infection positively predicted perceived susceptibility to infection and negatively predicted perceived vaccine effectiveness. Prior vaccination positively predicted perceived vaccine effectiveness and self-efficacy, and negatively predicted concerns about side effects. Information exposure via the government and television news was positively related to perceived severity of and susceptibility to illness and vaccination self-efficacy. There were three notable mediation effects in the prediction of booster intention. The effect of prior infection was mediated by perceived vaccine effectiveness and the effect of prior vaccination was mediated by perceived vaccine effectiveness and perceived severity of vaccine side effects. These findings suggest that personal vaccination history and beliefs about vaccine effectiveness and safety may be especially important for promoting booster uptake.