Possible contribution of COVID-19 vaccination to the subsequent mental well-being in Japan

The coronavirus disease 2019 (COVID-19) pandemic has had a severe impact on mental well-being. Vaccination may have played a pivotal role in enduring this mental health crisis. The present study aimed to longitudinally investigate the association between COVID-19 vaccination and mental health status among Japanese population in 2021. Longitudinal data of 17,089 individuals aged 15-79 years who participated in a nationwide online study were analyzed. Baseline and follow-up mental health statuses were assessed using the Kessler Psychological Distress Scale (K6). General linear and multivariable logistic regression models adjusted for baseline levels of mental distress were used to examine the association between vaccine receipt and follow-up levels of mental health. Mean K6 scores were lower in the vaccinated than in the non-vaccinated participants. Those who had received one or two doses of COVID-19 vaccines were associated with improved mental health at follow-up in subjects with psychological distress at baseline (odds ratio [OR] 1.31 and 1.35, respectively) and were inversely associated with deteriorated mental health status at follow-up in subjects without psychological distress at baseline (OR 0.66 and 0.70, respectively) compared with no vaccination groups, respectively. The present study would indicate that one or two doses of COVID-19 vaccinations contributed to mental well-being in Japan. This finding might provide evidence for promoting vaccination against COVID-19 and emerging infectious diseases in the future.