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

Objective 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. Design Retrospective observational study. Setting Tertiary care centre in Japan. Participants All patients diagnosed with COVID-19 who were hospitalised between January 2020 and April 2022 were included. Measurements Clinical characteristics, characteristics of admission, treatments and outcomes were investigated and compared among six pandemic waves. Results 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. Conclusions 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.