Abstract
The Japanese government implemented a large-scale vaccination policy against the coronavirus disease 2019 (COVID-19) pandemic, primarily using messenger RNA vaccines in 2021. Its hallmark was prioritized vaccination for the elderly after healthcare workers in a short period of time. Vaccination for the elderly, vulnerable to infection and severe disease, was carried out rapidly in approximately 4 months since April 2021. We evaluated the impact of Japan's vaccination policy against COVID-19 during the pandemic, with a particular focus on how prioritized vaccination for the elderly affected the pandemic. We observed a remarkable decrease in the number of infections, cluster events in long-term care facilities, and severe disease among the elderly during the fifth wave (August 2021) despite rising incidence of infections in the overall population. In conclusion, we think that prioritized vaccination for the elderly was efficacious in preventing infections and severe COVID-19 among the elderly during the fifth wave in Japan.