1. 1. Ministry of Health, Labour, and Welfare of Japan. Visualizing the data: Information on COVID-19 infections. https://covid19.mhlw.go.jp/en/ (accessed February 28, 2022).
2. 2. Ministry of Health, Labour, and Welfare of Japan. 11 pieces of knowledge about COVID-19 “now," as of February 2022 https://www.mhlw.go.jp/content/000788485.pdf (accessed February 28, 2022). (in Japanese)
3. 3. National Institute of Infectious Diseases of Japan. The mutant strain B.1.1.529 (Omicron strain) of SARS CoV-2, 7th report. https://www.niid.go.jp/niid/ja/2019-ncov/2551-cepr/10945-sars-cov-2-b-1-1-529-7.html (accessed February 28, 2022). (in Japanese)
4. 4. Government Announcement by the Cabinet Secretariat of Japan. "Indicators and Guidelines for the Implementation of Countermeasures in Response to Future Changes in the Status of Infection" August 7, 2020. https://corona.go.jp/news/pdf/jimurenraku_0811.pdf (accessed February 28, 2022). (in Japanese)
5. 5. Ministry of Health, Labour, and Welfare of Japan. Advisory Board for Countermeasures against COVID-19. https://www.mhlw.go.jp/stf/covid-19/seifunotorikumi.html#h2_3 (accessed February 28, 2022). (in Japanese)