1. 1) World Health Organization. “Global Influenza Programme.”: 〈https://www.who.int/teams/global-influenza-programme/vaccines?gclid=EAIaIQobChMI-sS7u6Cy-wIVyCFgCh2NQAiwEAAYASACEgJ5g_D_BwE〉, cited 16 November, 2022.
2. 2) World Health Organization. “Influenza (Seasonal).”: 〈https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)〉, cited 16 November, 2022.
3. 3) Saitoh A., Okabe N., Vaccine, 39, 3018–3024 (2021).
4. 4) Ministry of Health, Labour and Welfare. “Information of vaccination (Yobosesshu joho).”: 〈https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/kenkou/kekkaku-kansenshou/yobou-sesshu/index.html〉, cited 21 October, 2022.
5. 5) National Institute of Infectious Diseases. “Infectious Agents Surveillance Report.”: 〈https://www.niid.go.jp/niid/ja/typhi-m/iasr-reference/2545-related-articles/related-articles-501/10786-501r05.html〉, cited 11 November, 2022.