Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study

The coronavirus disease 2019 (COVID-19) pandemic has dramatically changed because of virus mutations, vaccine dissemination, treatment development and policies, among other factors. These factors have a dynamic and complex effect on the characteristics and outcomes of patients. Therefore, there is a...

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Main Authors: Koichi Miyashita, Hironao Hozumi, Kazuki Furuhashi, Eiji Nakatani, Yusuke Inoue, Hideki Yasui, Masato Karayama, Yuzo Suzuki, Tomoyuki Fujisawa, Noriyuki Enomoto, Naoki Inui, Toshiyuki Ojima, Takafumi Suda
Format: Article
Language:English
Published: Taylor & Francis Group 2023-12-01
Series:Emerging Microbes and Infections
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Online Access:https://www.tandfonline.com/doi/10.1080/22221751.2022.2155250
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author Koichi Miyashita
Hironao Hozumi
Kazuki Furuhashi
Eiji Nakatani
Yusuke Inoue
Hideki Yasui
Masato Karayama
Yuzo Suzuki
Tomoyuki Fujisawa
Noriyuki Enomoto
Naoki Inui
Toshiyuki Ojima
Takafumi Suda
author_facet Koichi Miyashita
Hironao Hozumi
Kazuki Furuhashi
Eiji Nakatani
Yusuke Inoue
Hideki Yasui
Masato Karayama
Yuzo Suzuki
Tomoyuki Fujisawa
Noriyuki Enomoto
Naoki Inui
Toshiyuki Ojima
Takafumi Suda
author_sort Koichi Miyashita
collection DOAJ
description The coronavirus disease 2019 (COVID-19) pandemic has dramatically changed because of virus mutations, vaccine dissemination, treatment development and policies, among other factors. These factors have a dynamic and complex effect on the characteristics and outcomes of patients. Therefore, there is an urgent need to understand those changes and update the evidence. We used a large-scale real-world data set of 937,758 patients with COVID-19 from a nationwide claims database that included outpatients and inpatients in Japan to investigate the changes in their characteristics, outcomes and risk factors for severity/mortality from the early pandemic to the delta variant-predominant waves. The severity of COVID-19 was defined according to the modified World Health Organization clinical-progression ordinal scale. With changing waves, mean patient age decreased, and proportion of patients with comorbidities decreased. The incidences of “severe COVID-19 or death (i.e. ≥severe COVID-19)” and “death” markedly declined (5.0% and 2.9%, wild-type-predominant; 4.6% and 2.2%, alpha variant-predominant and 1.4% and 0.4%, delta variant-predominant waves, respectively). Across the wave shift, risk factors for ≥ severe COVID-19 and death, including older age, male, malignancy, congestive heart failure and chronic obstructive pulmonary disease, were largely consistent. The significance of some factors, such as liver disease, varied as per the wave. This study, one of the largest population-based studies on COVID-19, showed that patient characteristics and outcomes changed during the waves. Risk factors for severity/mortality were similar across all waves, but some factors were inconsistent. These data suggest that the clinical status of COVID-19 will change further with the coming epidemic wave.
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spelling doaj-art-f33e820f9b1a46c39e5eaeebd5ef9da52025-08-20T01:49:50ZengTaylor & Francis GroupEmerging Microbes and Infections2222-17512023-12-0112110.1080/22221751.2022.2155250Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based studyKoichi Miyashita0Hironao Hozumi1Kazuki Furuhashi2Eiji Nakatani3Yusuke Inoue4Hideki Yasui5Masato Karayama6Yuzo Suzuki7Tomoyuki Fujisawa8Noriyuki Enomoto9Naoki Inui10Toshiyuki Ojima11Takafumi Suda12Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanGraduate School of Public Health, Shizuoka Graduate University of Public Health, Shizuoka, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanDepartment of Clinical Pharmacology and Therapeutics, Hamamatsu University School of Medicine, Hamamatsu, JapanDepartment of Community Health and Preventive Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanSecond Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, JapanThe coronavirus disease 2019 (COVID-19) pandemic has dramatically changed because of virus mutations, vaccine dissemination, treatment development and policies, among other factors. These factors have a dynamic and complex effect on the characteristics and outcomes of patients. Therefore, there is an urgent need to understand those changes and update the evidence. We used a large-scale real-world data set of 937,758 patients with COVID-19 from a nationwide claims database that included outpatients and inpatients in Japan to investigate the changes in their characteristics, outcomes and risk factors for severity/mortality from the early pandemic to the delta variant-predominant waves. The severity of COVID-19 was defined according to the modified World Health Organization clinical-progression ordinal scale. With changing waves, mean patient age decreased, and proportion of patients with comorbidities decreased. The incidences of “severe COVID-19 or death (i.e. ≥severe COVID-19)” and “death” markedly declined (5.0% and 2.9%, wild-type-predominant; 4.6% and 2.2%, alpha variant-predominant and 1.4% and 0.4%, delta variant-predominant waves, respectively). Across the wave shift, risk factors for ≥ severe COVID-19 and death, including older age, male, malignancy, congestive heart failure and chronic obstructive pulmonary disease, were largely consistent. The significance of some factors, such as liver disease, varied as per the wave. This study, one of the largest population-based studies on COVID-19, showed that patient characteristics and outcomes changed during the waves. Risk factors for severity/mortality were similar across all waves, but some factors were inconsistent. These data suggest that the clinical status of COVID-19 will change further with the coming epidemic wave.https://www.tandfonline.com/doi/10.1080/22221751.2022.2155250COVID-19epidemiologyrisk factorsnational database of health insurance claims and specific health checkups of JapanNDB
spellingShingle Koichi Miyashita
Hironao Hozumi
Kazuki Furuhashi
Eiji Nakatani
Yusuke Inoue
Hideki Yasui
Masato Karayama
Yuzo Suzuki
Tomoyuki Fujisawa
Noriyuki Enomoto
Naoki Inui
Toshiyuki Ojima
Takafumi Suda
Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
Emerging Microbes and Infections
COVID-19
epidemiology
risk factors
national database of health insurance claims and specific health checkups of Japan
NDB
title Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
title_full Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
title_fullStr Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
title_full_unstemmed Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
title_short Changes in the characteristics and outcomes of COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study
title_sort changes in the characteristics and outcomes of covid 19 patients from the early pandemic to the delta variant epidemic a nationwide population based study
topic COVID-19
epidemiology
risk factors
national database of health insurance claims and specific health checkups of Japan
NDB
url https://www.tandfonline.com/doi/10.1080/22221751.2022.2155250
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