{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T18:56:07Z","timestamp":1767898567591,"version":"3.49.0"},"reference-count":23,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T00:00:00Z","timestamp":1767830400000},"content-version":"unspecified","delay-in-days":7,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2025,12,21]]},"published-print":{"date-parts":[[2026,1]]},"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This study aims to describe the characteristics of hospitalised COVID-19 patients in a tertiary care hospital close to an international airport in Japan and to compare these characteristics among different waves during the pandemic.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design<\/jats:title>\n                    <jats:p>Retrospective observational study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>Tertiary care centre in Japan.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Participants<\/jats:title>\n                    <jats:p>All patients diagnosed with COVID-19 who were hospitalised between January 2020 and April 2022 were included.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Measurements<\/jats:title>\n                    <jats:p>Clinical characteristics, characteristics of admission, treatments and outcomes were investigated and compared among six pandemic waves.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>A total of 827 patients were included. The median age was 58.0 years. More than half of the patients (58.3%) had at least one comorbidity. The majority of patients (89.0%) were domestically infected patients admitted under the Infectious Diseases Law, while the remaining patients (11.0%) were those diagnosed during airport quarantine and admitted under the Quarantine Act. Hospital-acquired COVID-19 infection occurred in 7.0% of cases, and mainly during the sixth wave. Overall, some form of oxygen therapy, high-flow oxygen devices, invasive mechanical ventilation (IMV) and extracorporeal membrane oxygenation was provided in 46.3%, 10.4%, 4.5% and 1.5% of cases, respectively. Only 1.8% of patients were treated in the intensive care unit (ICU), and 59.5% of patients on IMV were managed in the non-ICU ward. The in-hospital mortality rate was 5.8%. Median age, percentages of some comorbidities, vaccination coverage, medications for COVID-19, types of supportive care and ICU admissions differed significantly among waves.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>This study suggests that patient characteristics, vaccination coverage, standard of treatment and severity of illness changed across waves during the COVID-19 pandemic. Intensive care delivery in non-ICU wards was unavoidable due to limited ICU capacity, which may be a key consideration when preparing for future pandemics.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2025-109380","type":"journal-article","created":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T13:40:41Z","timestamp":1767879641000},"page":"e109380","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Clinical characteristics, treatments and outcomes of hospitalised COVID-19 patients across pandemic waves at a tertiary acute care hospital in Narita, Japan: a single-centre retrospective observational study"],"prefix":"10.1136","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3135-1757","authenticated-orcid":false,"given":"Ryota","family":"Hase","sequence":"first","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Kameda Medical Center, Kamogawa, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rika","family":"Kurata","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Kameda Medical Center, Kamogawa, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yu","family":"Niiyama","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of General Internal Medicine, Matsuyama Red Cross Hospital, Matsuyama, Ehime, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Naoya","family":"Matsuda","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Embassy of Japan in Nigeria, Abuja, Nigeria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hideki","family":"Ueda","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Emergency Medicine and General Internal Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Koki","family":"Kikuchi","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Teine Keijinkai Hospital, Sapporo, Hokkaido, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Keiko","family":"Ishida","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Kameda Medical Center, Kamogawa, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yoshifumi","family":"Kubota","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Emergency and Critical Care Medicine, National Hospital Organization Nagasaki Medical Center, Omura, Nagasaki, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Motoki","family":"Fujii","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Kameda Medical Center, Kamogawa, Chiba, Japan"},{"name":"Department of Intensive Care Medicine, Kameda Medical Center, Kamogawa, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takashi","family":"Kurita","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Infectious Diseases, Institute of Science Tokyo, Bunkyo, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Emiri","family":"Muranaka","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hiroki","family":"Sasazawa","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Internal Medicine\/Infectious Diseases, Omachi Municipal General Hospital, Omachi, Nagano, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Haruki","family":"Mito","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yudai","family":"Yano","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Internal Medicine, Sekishinkan Hospital, Komatsushima, Tokushima, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Reiko","family":"Oku","sequence":"additional","affiliation":[{"name":"Department of Emergency and Critical Care Medicine, Japanese Red Cross Narita Hospital, Narita, Chiba, Japan"},{"name":"Department of Critical Care Medicine, Japanese Red Cross Kumamoto Hospital, Kumamoto, 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