Assessing the Lower Incidence of Invasive Pneumococcal Diseases in Japan During the COVOD-19 Pandemic.

During the COVID-19 pandemic from 2020 to 2023 in Japan, in our hospital there were seven cases of invasive pneumococcal diseases (IPDs) in this COVID-19 pandemic period although 14 IPD cases were treated in 2019, 2024, and 2025, such as pre-/post- COVID-19 pandemic period. Of these total 21 IPD patients, five (23.8%) died, and they were all treated during pre-/post-pandemic period. Only 2 of the 21 patients (9.5%) children had been vaccinated. Furthermore, compared with survivors, those who died were younger (54.0 vs 69.4 years old, p = 0.0011), had lower white blood cell counts (3672.1 vs 12117.3/µL, p = 0.0011), and had higher C-reactive protein levels (34.5 vs 22.1 mg/dL, p = 0.0010). Two or more bacteria were isolated, and multiple and/or broad antimicrobial agents were used in fatal cases. These data suggested that IPD cases decreased and might have been less pathogenic during the COVID-19 pandemic period than in the pre-/post-COVID-19 pandemic period. In addition, those who died were younger, more septic due to multiple bacterial infections, and received more and broader antimicrobial agents than survivors. No adult patients received pneumococcal vaccination, which suggests that low vaccination rates lead to the high mortality of adult IPD patients.