# Postpandemic Change in Demographic and Clinical Features of Patients With Omicron Who Were Hospitalized: Territory-Wide Retrospective Repeated Cross-Sectional Study in Hong Kong

## TL;DR

This study examines how the Omicron variant's impact on hospitalized patients in Hong Kong changed over time, including during the postpandemic period.

## Contribution

The study provides a territory-wide analysis of demographic and clinical shifts in Omicron cases across multiple waves and into the postpandemic era.

## Key findings

- Case fatality ratio decreased significantly among those over 85 years old during the Omicron waves.
- Females aged over 85 years were predominantly infected, and most patients were Chinese across all age groups.
- Hospital stays for Omicron patients decreased, and bronchodilator use increased during later periods.

## Abstract

The Omicron variant of SARS-CoV-2 underwent several mutations since it was first identified in November 2021, with a large outbreak in Hong Kong in early 2022. Yet, local cases of Omicron infections persist, even though the COVID-19 pandemic ended in May 2023.

This study aims to describe the changes in demographic and clinical characteristics of patients infected with COVID-19 across different Omicron waves in Hong Kong and determine whether the changes continued into the postpandemic period.

This retrospective repeated cross-sectional study collected data on patients infected with COVID-19 admitted to public hospitals in Hong Kong between May 1, 2022, and May 31, 2024. These data were later categorized into 3 periods based on the Omicron strain. A subsequent age-stratified descriptive analysis was conducted on each characteristic to identify any significant differences across the periods.

First, the case fatality ratio significantly lowered among those older than 85 years (1.5% proportion decrease, period 1: 11.6%, period 2: 10.1%, effect size: 0.02; P<.001). Second, most patients were Chinese (≥68.7% per age group and period), and females were predominantly infected for those aged older than 85 years (≥56.9% per period). Third, the Charlson Comorbidity Index scores in most age groups showed a predominant proportion of infected individuals with 0 scores (more than 70% per period). Fourth, most cases were from slightly disadvantaged populations in Hong Kong (≥30.5% per age group per period). Fifth, clinical management of Omicron hospitalizations showed lowered length of hospital stays among adults and older individuals (≥1 d decrease between periods 1 and 3, per age group), as well as increased administration of bronchodilators.

Despite the decreasing incidence of Omicron cases admitted to public hospitals in Hong Kong, the increasing case fatality ratio with age suggests that long-term surveillance of COVID-19 should be maintained to prepare for potential mutations and outbreaks.