Impact of prioritized vaccinations for the elderly on the COVID-19 pandemic in Japan

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.

Keywords: messenger RNA vaccines; pandemic; vaccination policy.

Figure 1.

Changes in vaccination rate for COVID-19 over time in 2021. The red dotted and solid lines represent one-and two-dose vaccination rates for the elderly, respectively. The black dotted and solid lines represent the one-and two-dose vaccination rates for the overall population, respectively.

Figure 2.

Number of newly confirmed COVID-19 patients over time in 2021. The blue and red lines represent the number of infections in the overall population and those aged ≥ 70 years, respectively. The black line represents the proportion of elderly patients among all patients.

Figure 3.

Number of severe diseases of COVID-19 over time in 2021. The blue and red lines represent the number of severe COVID-19 cases among the overall population and those aged ≥ 70 years, respectively. The black line represents the proportion of elderly patients among all patients. Patients with severe COVID-19 were defined as those who were on a ventilator or on extracorporeal membrane oxygenation or were treated in an ICU.

Figure 4.

Number of cluster events by different types of facilities over time in 2021. The red, blue, violet, gray, yellow, and green lines represent cluster events in the long-term care facilities for the elderly, medical institutions, schools, restaurants, sports facilities, and companies, respectively.