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Change over Time in the Risk of Death among Japanese COVID-19 Cases Caused by the Omicron Variant Depending on Prevalence of Sublineages

Author

Listed:
  • Yuki Takahashi

    (Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan)

  • Hideo Tanaka

    (Neyagawa City Public Health Center, Neyagawa 572-0838, Japan)

  • Yoshitaka Koga

    (Tosu Public Health and Welfare Office of Saga Prefectural Government, Tosu 841-0051, Japan)

  • Shunichi Takiguchi

    (Central Public Health Center of Miyazaki Prefectural Government, Kirishima 880-0032, Japan)

  • Shigeru Ogimoto

    (Miyoshi Public Health Center of Tokushima Prefectural Government, Mima 778-0002, Japan)

  • Shizuyo Inaba

    (Gifu Public Health Center of Gifu Prefectural Government, Gifu 504-0838, Japan)

  • Hiroyuki Matsuoka

    (Iida Public Health Center of Nagano Prefectural Government, Iida 395-0034, Japan)

  • Yuka Miyajima

    (Matsumoto Public Health Center of Nagano Prefectural Government, Matsumoto 390-0852, Japan)

  • Takeshi Takagi

    (Isesaki Public Health Center of Gunma Prefectural Government, Isesaki 372-0024, Japan)

  • Fujiko Irie

    (Tsuchiura Public Health Center of Ibaraki Prefectural Government, Tsuchiura 300-0812, Japan)

  • Yoshihito Bamba

    (Ibaraki Prefectual Department of Public Health and Welfare, Mito 310-8555, Japan)

  • Fuyo Yoshimi

    (Central Public Health Center of Ibaraki Prefectural Government, Mito 310-0852, Japan)

  • Tomoyuki Suzuki

    (Shiga Prefectural Department of Public Health Care and Welfare, Otsu 520-8577, Japan)

  • Isao Araki

    (Shiga Prefectural Health, Medical and Welfare Department, Otsu 520-8577, Japan)

  • Chika Shirai

    (Hirakata City Public Health Center, Hirakata 573-0027, Japan)

  • Sayuri Matsumoto

    (Higashiosaka City Public Health Center, Higashiosaka 578-0941, Japan)

  • Motoyuki Shimizu

    (Higashiosaka City Public Health Center, Higashiosaka 578-0941, Japan)

  • Toshiyuki Shibata

    (Suita City Public Health Center, Suita 564-0072, Japan)

  • Hitomi Nagai

    (Ibaraki Public Health Center of Osaka Prefectural Government, Ibaraki 567-8585, Japan)

  • Masaru Kinoshita

    (Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan)

  • Rie Fujita

    (Kenou Public Health Center of Nagasaki Prefectural Government, Isahaya 854-0081, Japan)

  • Tsuyoshi Ogata

    (Itako Public Health Center of Ibaraki Prefectural Government, Itako 311-2422, Japan)

Abstract

To assess temporal changes to the risk of death in COVID-19 cases caused by the Omicron variant, we calculated age-standardized case fatality rates (CFR) in patients aged ≥40 years over nine diagnostic periods (3 January to 28 August 2022) in ten Japanese prefectures (14.8 million residents). Among 552,581 study subjects, we found that there were 1836 fatalities during the isolation period (up to 28 days from date of onset). The highest age-standardized CFR (0.85%, 95% confidence interval (CI):0.78–0.92) was observed in cases diagnosed in the second 4-week period (January 31 to February 27), after which it declined significantly up to the 6th 4-week period (0.23%, 95% CI: 0.13–0.33, May 23 to June 19). The CFR then increased again but remained at 0.39% in the eighth period (July 18 to August 28). The CFR in cases with the BA.2 or BA.5 sublineages in the age range 60–80 years was significantly lower than that with BA.1 infections (60 years: 0.19%, 0.02%, 0.053%, respectively; 70 years: 0.91%, 0.33%, 0.39%; ≥80 years: 3.78%, 1.96%, 1.81%, respectively). We conclude that the risk of death in Japanese COVID-19 patients infected with Omicron variants declined through February to mid-June 2022.

Suggested Citation

  • Yuki Takahashi & Hideo Tanaka & Yoshitaka Koga & Shunichi Takiguchi & Shigeru Ogimoto & Shizuyo Inaba & Hiroyuki Matsuoka & Yuka Miyajima & Takeshi Takagi & Fujiko Irie & Yoshihito Bamba & Fuyo Yoshim, 2023. "Change over Time in the Risk of Death among Japanese COVID-19 Cases Caused by the Omicron Variant Depending on Prevalence of Sublineages," IJERPH, MDPI, vol. 20(4), pages 1-9, February.
    • Handle: RePEc:gam:jijerp:v:20:y:2023:i:4:p:2779-:d:1057921
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