Characteristics of hospitalized patients with COVID-19 during the first to fifth waves of infection: a report from the Japan COVID-19 Task Force
Authors: Lee Ho , Chubachi Shotaro , Namkoong Ho , Asakura Takanori , Tanaka Hiromu , Otake Shiro , Nakagawara Kensuke , Morita Atsuho , Fukushima Takahiro , Watase Mayuko , Kusumoto Tatsuya , Masaki Katsunori , Kamata Hirofumi , Ishii Makoto , Hasegawa Naoki , Harada Norihiro , Ueda Tetsuya , Ueda Soichiro , Ishiguro Takashi , Arimura Ken , Saito Fukuki , Yoshiyama Takashi , Nakano Yasushi , Mutoh Yoshikazu , Suzuki Yusuke , Murakami Koji , Okada Yukinori , Koike Ryuji , Kitagawa Yuko , Kimura Akinori , Imoto Seiya , Miyano Satoru , Ogawa Seishi , Kanai Takanori , Fukunaga Koichi ,   The Japan COVID-19 Task Force, Lee Ho , Chubachi Shotaro , Namkoong Ho , Asakura Takanori , Tanaka Hiromu , Otake Shiro , Nakagawara Kensuke , Morita Atsuho , Fukushima Takahiro , Watase Mayuko , Kusumoto Tatsuya , Masaki Katsunori , Kamata Hirofumi , Ishii Makoto , Hasegawa Naoki , Harada Norihiro , Ueda Tetsuya , Ueda Soichiro , Ishiguro Takashi , Arimura Ken , Saito Fukuki , Yoshiyama Takashi , Nakano Yasushi , Mutoh Yoshikazu , Suzuki Yusuke , Murakami Koji , Okada Yukinori , Koike Ryuji , Kitagawa Yuko , Kimura Akinori , Imoto Seiya , Miyano Satoru , Ogawa Seishi , Kanai Takanori , Fukunaga Koichi , Takahashi Kazuhisa , Naito Toshio , Hiki Makoto , Matsushita Yasushi , Takagi Haruhi , Aoki Ryousuke , Nakamura Ai , Harada Sonoko , Sasano Hitoshi , Masaki Katsunori , Ikemura Shinnosuke , Okamori Satoshi , Terai Hideki , Asakura Takanori , Sasaki Junichi , Morisaki Hiroshi , Uwamino Yoshifumi , Nanki Kosaku , Mikami Yohei , Uchida Sho , Uno Shunsuke , Ishihara Rino , Matsubara Yuta , Nishimura Tomoyasu , Ogawa Takunori , Sato Toshiro , Azuma Masanori , Saito Ryuichi , Sado Toshikatsu , Miyazaki Yoshimune , Sato Ryuichi , Haruta Yuki , Nagasaki Tadao , Yasui Yoshinori , Hasegawa Yoshinori , Tada Ai , Miyawaki Masayoshi , Yamamoto Masaomi , Yoshida Eriko , Hayashi Reina , Nagasaka Tomoki , Arai Sawako , Kaneko Yutaro , Sasaki Kana , Isono Taisuke , Shibata Shun , Matsui Yuma , Hosoda Chiaki , Takano Kenji , Nishida Takashi , Kobayashi Yoichi , Takaku Yotaro , Takayanagi Noboru , Tagaya Etsuko , Kawana Masatoshi , Nakamori Yasushi , Yoshiya Kazuhisa , Saito Fukuki , Yoshihara Tomoyuki , Wada Daiki , Iwamura Hiromu , Kanayama Syuji , Maruyama Shuhei , Hasegawa Takanori , Takahashi Kunihiko , Anzai Tatsuhiko , Ito Satoshi , Endo Akifumi , Uchimura Yuji , Miyazaki Yasunari , Honda Takayuki , Tateishi Tomoya , Tohda Shuji , Ichimura Naoya , Sonobe Kazunari , Sassa Chihiro Tani , Nakajima Jun , Ai Masumi , OhtaKokuto Ken Hiroyuki , Ogata Hideo , Tanaka Yoshiaki , Arakawa Kenichi , Shimoda Masafumi , Osawa Takeshi , Nakajima Yukiko , Anan Ryusuke , Arai Ryosuke , Kurihara Yuko , Harada Yuko , Nishio Kazumi , Sato Tomonori , Takei Reoto , Hagimoto Satoshi , Noguchi Yoichiro , Yamano Yasuhiko , Sasano Hajime , Ota Sho , Nakayama Sohei , Masuzawa Keita , Takano Tomomi , Katayama Kazuhiko , Murakami Koji , Yamada Mitsuhiro , Sugiura Hisatoshi , Sano Hirohito , Matsumoto Shuichiro , Kimura Nozomu , Ono Yoshinao , Baba Hiroaki , Baba Rie , Arai Daisuke , Ogura Takayuki , Takahashi Hidenori , Hagiwara Shigehiro , Nagao Genta , Konishi Shunichiro , Nakachi Ichiro , Tateno Hiroki , Hase Isano , Yoshida Shuichi , Suzuki Shoji , Kawada Miki , Horinouchi Hirohisa , Saito Fumitake , Mitamura Keiko , Hagihara Masao , Ochi Junichi , Uchida Tomoyuki , Edahiro Ryuya , Shirai Yuya , Sonehara Kyuto , Naito Tatsuhiko , Yamamoto Kenichi , Namba Shinichi , Suzuki Ken , Shiroyama Takayuki , Maeda Yuichi , Nii Takuro , Noda Yoshimi , Niitsu Takayuki , Adachi Yuichi , Enomoto Takatoshi , Amiya Saori , Hara Reina , Sasa Noa , Yamada Shuhei , Kishikawa Toshihiro , Tomono Kazunori , Yamada Kazuto Kato Shuhei , Ueno Yuya , Suzuki Motoyuki , Takemoto Norihiko , Eguchi Hirotaka , Fukusumi Takahito , Imai Takao , Fukushima Munehisa , Takagaki Masatoshi , Kishima Haruhiko , Inohara Hidenori , Hirata Haruhiko , Takeda Yoshito , Kumanogoh Atsushi , Miyazawa Naoki , Kimura Yasuhiro , Sado Reiko , Sugimoto Hideyasu , Kamiya Akane , Kuwahara Naota , Fujiwara Akiko , Matsunaga Tomohiro , Sato Yoko , Okada Takenori , Inoue Takashi , Hirano Toshiyuki , Kobayashi Keigo , Takaoka Hatsuyo , Nishi Koichi , Nishitsuji Masaru , Tani Mayuko , Suzuki Junya , Nakatsumi Hiroki , Koh Hidefumi , Manabe Tadashi , Funatsu Yohei , Ito Fumimaro , Fukui Takahiro , Shinozuka Keisuke , Kohashi Sumiko , Miyazaki Masatoshi , Shoko Tomohisa , Kojima Mitsuaki , Adachi Tomohiro , Ishikawa Motonao , Takahashi Kenichiro , Watanabe Kazuyoshi , Hirai Yoshihiro , Kawashima Hidetoshi , Narita Atsuya , Niwa Kazuki , Sekikawa Yoshiyuki , Sageshima Hisako , Nakamura Yoshihiko , Hoshino Kota , Maruyama Junichi , Ishikura Hiroyasu , Takata Tohru , Ogura Takashi , Kitamura Hideya , Hagiwara Eri , Murohashi Kota , Okabayashi Hiroko , Mochimaru Takao , Nukaga Shigenari , Satomi Ryosuke , Oyamada Yoshitaka , Mori Nobuaki , Baba Tomoya , Fukui Yasutaka , Odate Mitsuru , Mashimo Shuko , Makino Yasushi , Yagi Kazuma , Hashiguchi Mizuha , Kagyo Junko , Shiomi Tetsuya , Kawamura Kodai , Ichikado Kazuya , Nishiyama Kenta , Muranaka Hiroyuki , Nakamura Kazunori , Fuke Satoshi , Saito Hiroshi , Tsuchida Tomoya , Fujitani Shigeki , Takita Mumon , Morikawa Daiki , Yoshida Toru , Izumo Takehiro , Inomata Minoru , Kuse Naoyuki , Awano Nobuyasu , Tone Mari , Ito Akihiro , Odani Toshio , Amishima Masaru , Hattori Takeshi , Shichinohe Yasuo , Kagaya Takashi , Kita Toshiyuki , Ohta Kazuhide , Sakagami Satoru , Koshida Kiyoshi , Nakamura Morio , Yokote Koutaro , Nakada Taka-Aki , Abe Ryuzo , Oshima Taku , Shimada Tadanaga , Hayashi Kentaro , Shimizu Tetsuo , Kozu Yutaka , Hiranuma Hisato , Gon Yasuhiro , Izumi Namiki , Nagata Kaoru , Ueda Ken , Taki Reiko , Hanada Satoko , Hashimoto Naozumi , Wakahara Keiko , Sakamoto Koji , Omote Norihito , Ando Akira , Kusaka Yu , Ohba Takehiko , Isogai Susumu , Ogawa Aki , Inoue Takuya , Kodama Nobuhiro , Kaneyama Yasunari , Maeda Shunsuke , Kuraki Takashige , Matsumoto Takemasa , Harada Masahiro , Takahashi Takeshi , Ono Hiroshi , Sakurai Toshihiro , Shibusawa Takayuki , Kawamura Yusuke , Nakayama Akiyoshi , Matsuo Hirotaka , Kimizuka Yoshifumi , Kawana Akihiko , Sano Tomoya , Watanabe Chie , Suematsu Ryohei , Masuda Makoto , Wakabayashi Aya , Watanabe Hiroki , Ueda Suguru , Nishikawa Masanori , YoshifujiIto Ayumi Kazuto , Takahashi Saeko , Ishioka Kota , Chihara Yusuke , Takeuchi Mayumi , Onoi Keisuke , Shinozuka Jun , Sueyoshi Atsushi , Nagasaki Yoji , Okamoto Masaki , Tokunaga Yoshihisa , Ishihara Sayoko , Shimo Masatoshi , Watanabe Masafumi , Inoue Sumito , Igarashi Akira , Sato Masamichi , Hizawa Nobuyuki , Inoue Yoshiaki , Chiba Shigeru , Yamagata Kunihiro , Kai Hirayasu , Hiramatsu Yuji , Fukuyama Satoru , Kan-o Keiko , Matsumoto Koichiro , Eriguchi Yoshihiro , Yonekawa Akiko , Kanaoka Kensuke , Ihara Shoichi , Komuta Kiyoshi , Asano Koichiro , Oguma Tsuyoshi , Ito Yoko , Hashimoto Satoru , Yamasaki Masaki , Kasamatsu Yu , Komase Yuko , Hida Naoya , Tsuburai Takahiro , Oyama Baku , Kitagawa Yuichiro , Fukuta Tetsuya , Miyake Takahito , Yoshida Shozo , Ogura Shinji , Takada Minoru , Kanda Hidenori , Abe Shinji , Kono Yuta , Togashi Yuki , Takoi Hiroyuki , Kikuchi Ryota , Ogawa Shinichi , Ogata Tomouki , Ishihara Shoichiro , Kanehiro Arihiko , Ozaki Shinji , Fuchimoto Yasuko , Wada Sae , Fujimoto Nobukazu , Nishiyama Kei , Terashima Mariko , Beppu Satoru , Yoshida Kosuke , Narumoto Osamu , Nagai Hideaki , Ooshima Nobuharu , Motegi Mitsuru , Umeda Akira , Miyagawa Kazuya , Shimada Hisato , Endo Mayu , Ohira Yoshiyuki , Sagara Hironori , Tanaka Akihiko , Ohta Shin , Kimura Tomoyuki , Shibata Yoko , Tanino Yoshinori , Nikaido Takefumi , Minemura Hiroyuki , Sato Yuki , Yamada Yuichiro , Hashino Takuya , Shinoki Masato , Iwagoe Hajime , Takahashi Hiroshi , Fujii Kazuhiko , Kishi Hiroto , Ishii Tomoo , Kanai Masayuki , Imamura Tomonori , Yamashita Tatsuya , Yatomi Masakiyo , Maeno Toshitaka , Hayashi Shinichi , Takahashi Mai , Kuramochi Mizuki , Kamimaki Isamu , Tominaga Yoshiteru , Utsugi Mitsuyoshi , Ono Akihiro , Tanaka Toru , Kashiwada Takeru , Fujita Kazue , Saito Yoshinobu , Seike Masahiro , Kanai Masahiro , Saiki Ryunosuke , Nannya Yasuhito , Hyugaji Takayoshi , Shimizu Eigo , Katayama Kotoe , Miyawaki Satoru , Takahashi Meiko , Matsuda Fumihiko , Omae Yosuke , Tokunaga Katsushi , Ueno Takafumi 
Published: December 2022

Abstract
Background
We aimed to elucidate differences in the characteristics of patients with coronavirus disease 2019 (COVID-19) requiring hospitalization in Japan, by COVID-19 waves, from conventional strains to the Delta variant.

Methods
We used secondary data from a database and performed a retrospective cohort study that included 3261 patients aged ≥ 18 years enrolled from 78 hospitals that participated in the Japan COVID-19 Task Force between February 2020 and September 2021.

Results
Patients hospitalized during the second (mean age, 53.2 years [standard deviation {SD}, ± 18.9]) and fifth (mean age, 50.7 years [SD ± 13.9]) COVID-19 waves had a lower mean age than those hospitalized during the other COVID-19 waves. Patients hospitalized during the first COVID-19 wave had a longer hospital stay (mean, 30.3 days [SD ± 21.5], p < 0.0001), and post-hospitalization complications, such as bacterial infections (21.3%, p < 0.0001), were also noticeable. In addition, there was an increase in the use of drugs such as remdesivir/baricitinib/tocilizumab/steroids during the latter COVID-19 waves. In the fifth COVID-19 wave, patients exhibited a greater number of presenting symptoms, and a higher percentage of patients required oxygen therapy at the time of admission. However, the percentage of patients requiring invasive mechanical ventilation was the highest in the first COVID-19 wave and the mortality rate was the highest in the third COVID-19 wave.

Conclusions
We identified differences in clinical characteristics of hospitalized patients with COVID-19 in each COVID-19 wave up to the fifth COVID-19 wave in Japan. The fifth COVID-19 wave was associated with greater disease severity on admission, the third COVID-19 wave had the highest mortality rate, and the first COVID-19 wave had the highest percentage of patients requiring mechanical ventilation.