Vaccination behavior under uncertainty: A longitudinal study on factors associated with COVID-19 vaccination behavior in Japan with focus on the effect of close others’ vaccination behavior

Experiencing apprehension and uncertainty toward the newly developed COVID-19 vaccines may be natural, but having people receive the vaccination is crucial in managing the pandemic. The present study aimed to examine how the beliefs, attitudes, and how the change in close others’ vaccination behavior from the beginning of the vaccine distribution predict the COVID-19 vaccine behavior today among Japanese sample. We conducted a longitudinal web-based survey at three time points between May 14-16, 2021 and August 12-18, 2022. At time 3, there were 1046 participants (mean age = 48.81, SD = 14.07, range = 20-80). 73% of the participants had received three or more shots at time 3, and when conducting ordinal logistic regression with intercept and slope of “Do you know anyone close to you who got vaccinated for COVID-19?” and intercept and slope of “Do you know anyone close to you who is saying they will not get vaccinated for COVID-19?,” COVID-19 vaccine uncertainty, COVID-19 risk perception, social norm of COVID-19 vaccination, COVID-19 vaccine attitude, gender, age, health status, impact of COVID-19 on life, experiences of testing positive for COVID-19, general vaccine attitude, knowledge of COVID-19 and big-five personality factors, the two intercepts were the two crucial factors in predicting later vaccination behaviors in relation with other factors. The result indicates that regardless of what attitudes people have toward vaccines, the initial status of the close others’ behavior is related relatively strongly to individuals’ vaccination behavior one and three months later.