Fig. 1

Trend of critical care demands and overall medical demands in Japan. The solid blue line represents the total number of severe COVID-19 patients divided by number of beds for severe COVID-19 patients × 100 (%) (critical care demands), and the solid green line represents the number of newly infected patients divided by the number of hospitalized beds for COVID-19 × 100 (%) (overall medical demands). The blue and green dotted lines represent 100% of each. This data was collected from the national database officially published by the Japanese government [16, 17]. During the study period, the following time frames were designated as epidemic waves based on Japanese public standards [20]: June 14, 2020 to October 9, 2020 was referred to as the “second wave,” October 10, 2020 to February 28, 2021 as the “third wave,” March 1, 2021 to June 20, 2021 as the “fourth wave,” June 21, 2021 to December 16, 2021 as the “fifth wave,” December 17, 2021 to June 24, 2022 as the “sixth wave,” June 25, 2022 to September 26, 2022 as the “seventh wave,” and September 27, 2022 onwards as the “eighth wave”