Outcomes of COVID-19 in the Omicron-predominant Wave: Large-scale Real-world Data Analysis with a Comparison to Influenza

Overview

Journal Pneumonia (Nathan)

Publisher Biomed Central

Date 2025 Feb 5

PMID 39905566

Authors

Koichi Miyashita

Hironao Hozumi

Kazuki Furuhashi

Eiji Nakatani

Yusuke Inoue

Hideki Yasui

Yuzo Suzuki

Masato Karayama

Noriyuki Enomoto

Tomoyuki Fujisawa

Naoki Inui

Toshiyuki Ojima

Takafumi Suda

Affiliations

Soon will be listed here.

Abstract

Purpose: Studies on COVID-19 mortality during the Omicron-predominant wave have focused primarily on the inpatient/emergency room setting, and real-world data including both inpatients and outpatients are lacking.

Methods: Patients diagnosed with COVID-19 (n = 27,440,148) or influenza (n = 8,179,641) from January 2020 to April 2023 were identified using nationwide claims data in Japan. Patients with COVID-19 in the Omicron-predominant wave were compared with their counterparts in earlier waves, and a subset of the former group (May 2022-April 2023) was compared with patients with influenza as controls.

Results: The mortality rates (average number of deaths/cases per week) of COVID-19 decreased over time, being 2.7% (169/6312), 2.1% (397/18,754), 0.7% (195/28,273), and 0.4% (1613/378,848) in the wild-type-, Alpha-, Delta-, and Omicron-predominant waves, respectively. However, the number of deaths increased substantially in the Omicron-predominant wave, especially among the elderly (e.g., in the Delta- and Omicron-predominant waves, the average numbers of deaths/cases per week were < 1/5527 (< 0.01%) and 4/105,763 (< 0.01%) respectively, in patients aged 0-19, versus 101/925 (10.9%) and 1212/20,771 (5.8%), respectively, in patients aged ≥ 80). The mortality rate was lower for patients with COVID-19 than in those with influenza among those aged ≤ 39 years but higher among those aged ≥ 40 years.

Conclusions: In the Omicron-predominant wave, the mortality rate of COVID-19 decreased, but the number of patients increased, leading to a substantial increase in the number of deaths, especially among the elderly. The mortality rate of COVID-19 was higher than that of influenza in the elderly but not in the young, highlighting the need for age-specific interventions.

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