tetano
Editor, Senior Moderator
Respir Investig
. 2026 May 12;64(4):101444.
doi: 10.1016/j.resinv.2026.101444. Online ahead of print.
Clinical manifestations of adult patients requiring influenza-associated hospitalization in the pre-, during, and post-COVID-19 pandemic periods: An internet-based, prospective, multicenter, cohort study in Japan
Masafumi Seki[SUP] 1 [/SUP], Akihiro Ito[SUP] 2 [/SUP], Yukiko Oya[SUP] 3 [/SUP], Yuki Shiko[SUP] 4 [/SUP], Maiko Osawa[SUP] 4 [/SUP], Kazuhiro Tateda[SUP] 5 [/SUP], Jiro Fujita[SUP] 6 [/SUP], Kosaku Komiya[SUP] 7 [/SUP], Akihiko Kawana[SUP] 8 [/SUP], Koichi Izumikawa[SUP] 9 [/SUP], Toshiaki Kikuchi[SUP] 10 [/SUP], Norio Ohmagari[SUP] 11 [/SUP], Mitsuhiro Yamada[SUP] 12 [/SUP], Takaya Maruyama[SUP] 13 [/SUP], Takahiro Takazono[SUP] 9 [/SUP], Makoto Miki[SUP] 14 [/SUP], Yoshitsugu Miyazaki[SUP] 15 [/SUP], Yoshitaka Yamazaki[SUP] 16 [/SUP], Hiroshi Kakeya[SUP] 17 [/SUP], Yuta Hayashi[SUP] 18 [/SUP], Hideaki Nagai[SUP] 19 [/SUP], Tadashi Ishida[SUP] 2 [/SUP]
Affiliations
Background: Influenza is a major concern, but it has been affected by the COVID-19 pandemic worldwide. The objective of this study was to clarify the differences in the clinical manifestations of severely ill patients infected with influenza in Japan among the pre-, during, and post-COVID-19 pandemic periods.
Methods: The clinical data of patients who were severely ill with influenza and required hospitalization were gathered and analyzed between September 2019 and August 2025 (6 influenza seasons) using an internet-based data-capture system, and the pre-(2019 season), during (2020, 2021, and 2022 seasons), and post- (2023 and 2024 seasons) COVID-19 pandemic periods were compared.
Results: A total of 490 patients were enrolled and analyzed, with 87 (17.8%), 21 (4.29%), and 382 (78.5%) patients in the pre-, during, and post-COVID-19 pandemic periods, with mortality of 2.3%, 0%, and 7.9%, respectively. Age, male/female ratio, underlying diseases, pneumonia rates, oxygen use, isolated bacteria, including Streptococcus pneumoniae, and anti-influenza agents were similar among the three groups. However, intrafamilial transmission was decreased, although the influenza vaccination rate and antibiotic use were decreased in the post-COVID-19 period.
Conclusions: Influenza infection might be a greater issue after the COVID-19 pandemic because of the decreased vaccination rate and worse prognosis in the post-COVID-19 period. Although intrafamilial transmission and antibiotic use were decreased in the post-COVID-19 period, continuous nationwide surveillance and promotion of vaccination will be required to inhibit the increase of hospitalized and/or severe influenza patients.
Keywords: Influenza; Intrafamilial transmission; Pneumonia; Streptococcus pneumoniae; Vaccine.
. 2026 May 12;64(4):101444.
doi: 10.1016/j.resinv.2026.101444. Online ahead of print.
Clinical manifestations of adult patients requiring influenza-associated hospitalization in the pre-, during, and post-COVID-19 pandemic periods: An internet-based, prospective, multicenter, cohort study in Japan
Masafumi Seki[SUP] 1 [/SUP], Akihiro Ito[SUP] 2 [/SUP], Yukiko Oya[SUP] 3 [/SUP], Yuki Shiko[SUP] 4 [/SUP], Maiko Osawa[SUP] 4 [/SUP], Kazuhiro Tateda[SUP] 5 [/SUP], Jiro Fujita[SUP] 6 [/SUP], Kosaku Komiya[SUP] 7 [/SUP], Akihiko Kawana[SUP] 8 [/SUP], Koichi Izumikawa[SUP] 9 [/SUP], Toshiaki Kikuchi[SUP] 10 [/SUP], Norio Ohmagari[SUP] 11 [/SUP], Mitsuhiro Yamada[SUP] 12 [/SUP], Takaya Maruyama[SUP] 13 [/SUP], Takahiro Takazono[SUP] 9 [/SUP], Makoto Miki[SUP] 14 [/SUP], Yoshitsugu Miyazaki[SUP] 15 [/SUP], Yoshitaka Yamazaki[SUP] 16 [/SUP], Hiroshi Kakeya[SUP] 17 [/SUP], Yuta Hayashi[SUP] 18 [/SUP], Hideaki Nagai[SUP] 19 [/SUP], Tadashi Ishida[SUP] 2 [/SUP]
Affiliations
- PMID: 42119417
- DOI: 10.1016/j.resinv.2026.101444
Background: Influenza is a major concern, but it has been affected by the COVID-19 pandemic worldwide. The objective of this study was to clarify the differences in the clinical manifestations of severely ill patients infected with influenza in Japan among the pre-, during, and post-COVID-19 pandemic periods.
Methods: The clinical data of patients who were severely ill with influenza and required hospitalization were gathered and analyzed between September 2019 and August 2025 (6 influenza seasons) using an internet-based data-capture system, and the pre-(2019 season), during (2020, 2021, and 2022 seasons), and post- (2023 and 2024 seasons) COVID-19 pandemic periods were compared.
Results: A total of 490 patients were enrolled and analyzed, with 87 (17.8%), 21 (4.29%), and 382 (78.5%) patients in the pre-, during, and post-COVID-19 pandemic periods, with mortality of 2.3%, 0%, and 7.9%, respectively. Age, male/female ratio, underlying diseases, pneumonia rates, oxygen use, isolated bacteria, including Streptococcus pneumoniae, and anti-influenza agents were similar among the three groups. However, intrafamilial transmission was decreased, although the influenza vaccination rate and antibiotic use were decreased in the post-COVID-19 period.
Conclusions: Influenza infection might be a greater issue after the COVID-19 pandemic because of the decreased vaccination rate and worse prognosis in the post-COVID-19 period. Although intrafamilial transmission and antibiotic use were decreased in the post-COVID-19 period, continuous nationwide surveillance and promotion of vaccination will be required to inhibit the increase of hospitalized and/or severe influenza patients.
Keywords: Influenza; Intrafamilial transmission; Pneumonia; Streptococcus pneumoniae; Vaccine.