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. 2022 Dec;11(1):2800-2807.
doi: 10.1080/22221751.2022.2128435.

Estimation of disease burden and clinical severity of COVID-19 caused by Omicron BA.2 in Shanghai, February-June 2022

Xinhua Chen  1   2 , Xuemei Yan  1   2 , Kaiyuan Sun  3 , Nan Zheng  1   2 , Ruijia Sun  1   2 , Jiaxin Zhou  1   2 , Xiaowei Deng  1   2 , Tingyu Zhuang  1   2 , Jun Cai  1   2 , Juanjuan Zhang  1   2 , Marco Ajelli  4 , Hongjie Yu  1   2
Affiliations

Estimation of disease burden and clinical severity of COVID-19 caused by Omicron BA.2 in Shanghai, February-June 2022

Xinhua Chen et al. Emerg Microbes Infect. 2022 Dec.

Abstract

An outbreak of COVID-19 caused by the SARS-CoV-2 Omicron BA.2 sublineage occurred in Shanghai, China from February 26 to June 30, 2022. We use official reported data retrieved from Shanghai municipal Health Commissions to estimate the incidence of infections, severe/critical infections, and deaths to assess the disease burden. By adjusting for right censoring and RT-PCR sensitivity, we provide estimates of clinical severity, including the infection fatality ratio, symptomatic case fatality ratio, and risk of developing severe/critical disease upon infection. The overall infection rate, severe/critical infection rate, and mortality rate were 2.74 (95% CI: 2.73-2.74) per 100 individuals, 6.34 (95% CI: 6.02-6.66) per 100,000 individuals and 2.42 (95% CI: 2.23-2.62) per 100,000 individuals, respectively. The severe/critical infection rate and mortality rate increased with age, noted in individuals aged 80 years or older. The overall fatality ratio and risk of developing severe/critical disease upon infection were 0.09% (95% CI: 0.09-0.10%) and 0.27% (95% CI: 0.24-0.29%), respectively. Having received at least one vaccine dose led to a 10-fold reduction in the risk of death for infected individuals aged 80 years or older. Under the repeated population-based screenings and strict intervention policies implemented in Shanghai, our results found a lower disease burden and mortality of the outbreak compared to other settings and countries, showing the impact of the successful outbreak containment in Shanghai. The estimated low clinical severity of this Omicron BA.2 epidemic in Shanghai highlight the key contribution of vaccination and availability of hospital beds to reduce the risk of death.

Keywords: COVID-19; Omicron BA.2; Shanghai; clinical severity; disease burden.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Spectrum of COVID-19 and primary outcomes.
Figure 2.
Figure 2.
Infection rate, severe/critical infection rate and mortality rate of COVID-19 caused by SARS-CoV-2 Omicron in Shanghai A) Infection rate (per 100 individuals); B) Severe/critical infection rate (per 100,000 individuals); C) Mortality rate (per 100,000 individuals).
Figure 3.
Figure 3.
Adjusted IFR and ISR of COVID-19 caused by SARS-CoV-2 Omicron in Shanghai A) IFR; B) ISR. The number represents the median estimates, and the error bar represents the 95% confidence interval.
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