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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.
Acknowledgements
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the NIH. This study was supported by grants from the Key Programme of the National Natural Science Foundation of China (grant 82130093 to H.Y.). The funders had no role in the study design, data collection, data analysis, data interpretation or writing of the report.
Contributors
H.Y. conceived, designed, and supervised the study. X.C., X.Y., N.Z., R.S., J.Z., W.L. and T.Z. collected and checked the data. X.C., X.Y., J.Z. and N.Z. analysed the data. X.C. wrote the first draft of the manuscript. X.C., K.S., J.C., J.Z., X.D., M.A. and H.Y. interpreted the results and revised the content critically. All authors approved the final version for submission and agreed to be accountable for all aspects of the work.
Data sharing
The data and code that support the findings of this study will be made available in GitHub upon manuscript acceptance.
Declaration of interests
H.Y. has received research funding from Sanofi Pasteur, GlaxoSmithKline, Yichang HEC Changjiang Pharmaceutical Company, Shanghai Roche Pharmaceutical Company, and SINOVAC Biotech Ltd. M.A. has received research funding from Seqirus. None of the research funding is related to this work. All other authors report no competing interests.
Disclaimer
The views expressed are those of the authors and do not necessarily represent the institutions with which the authors are affiliated.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Role of the funding source
The funder of the study had no role in the study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding authors had full access to all the data in the study and had final responsibility for the decision to submit for publication. This study was approved by the institutional review board of the School of Public Health, Fudan University (IRB# 2022-05-0968). All data were collected from publicly available sources. Data were deidentified, and the need for informed consent was waived.