Factors affecting motivation for receiving a booster dose of the COVID-19 vaccine among Japanese university students and staff: a cross-sectional questionnaire survey.

Understanding the factors that influence people's decisions regarding vaccination is essential to promote vaccination. We aimed to clarify the motivations for receiving booster vaccines. We conducted a paper-based questionnaire distributed during January-February 2022 involving students and faculty staff who received the first COVID-19 vaccination at the mass vaccination program during June-September 2021 at Keio University. A total of 1725 participants were enrolled, and all completed the survey. Among these, 64.9% reported a significant adverse event (AEs) affecting daily life after the second vaccine. "Fear of severe COVID-19 illness" (72.6%) was the most common reason for getting vaccinated, followed by "concern of infecting others" (68.4%) and "fear of COVID-19 infection itself" (68.3%). Television emerged as the most influential source of information (80%), followed by university information (50.2%) and social networking sites (42.8%). Multivariate analysis revealed "fear of severe COVID-19 illness", "fear of COVID-19 infection itself", and "trust in the efficacy and safety of the vaccines in general" were significantly correlated with willingness to receive paid vaccinations. The severity of AEs and source of information were not related to participants' willingness to receive booster vaccinations. Participants with positive reasons for vaccination were more likely to accept a third dose.