Characteristics of hospitalized patients with COVID-19 during the first to fifth waves of infection: a report from the Japan COVID-19 Task Force

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.

Prognostic significance of chronic kidney disease and impaired renal function in Japanese patients with COVID-19

“…Third, this study did not assess the SARS-CoV-2 variant or collect complete information on patient vaccination status. However, we have already confirmed the stratified analysis based on the epidemic waves in Japan as reported [ 33 , 34 ], and an analysis stratified by these epidemic waves corresponded to the viral variants in this study, confirming the robustness of the results. Future studies should consider stratifying the analysis according to the epidemics wave or viral variants.…”

Characteristics and clinical effectiveness of COVID-19 vaccination in hospitalized patients in Omicron-dominated epidemic wave – a nationwide study in Japan

“…Vaccination commenced from February 2021, sotrovimab and molnupiravir became newly available as antiviral drugs, and early administration of remdesivir to prevent disease exacerbation became available in the middle of the sixth wave. We compared clinical information on the first five waves in Japan and reported the high severity of the fifth wave, which was mainly caused by the Delta strain [1] . Although there are limited reports on the clinical characteristics and vaccine effects in hospitalized patients during the Omicron epidemic in 2022, we aimed to compare clinical characteristics and outcome on hospitalized patients from Delta- vs Omicron-dominated waves and evaluated the association between vaccination and disease severity in the Omicron-dominated wave.…”

Characteristics of patients with COVID-19 who have deteriorating chest X-ray findings within 48 hours: a retrospective cohort study

“…First, we could not determine the mechanisms underlying rapid deterioration of CXR ndings from a virological perspective. Therefore, our ndings may not re ect the current clinical picture of COVID-19 since epidemics of different variants have become serious public health threats in Japan and other countries [40,41]. Second, since this was a multi-centre study, the interpretation of radiograms may have differed among centres.…”