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Review
. 2022 Jun 30;10(7):1049.
doi: 10.3390/vaccines10071049.

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

Weijing Shang  1 , Liangyu Kang  1 , Guiying Cao  1 , Yaping Wang  1 , Peng Gao  1 , Jue Liu  1 , Min Liu  1
Affiliations
Review

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

Weijing Shang et al. Vaccines (Basel). .

Abstract

Background: Asymptomatic infections are potential sources of transmission for coronavirus disease 2019, especially during the epidemic of the SARS-CoV-2 Omicron variant. We aimed to assess the percentage of asymptomatic infections among SARS-CoV-2 Omicron variant-positive individuals detected by gene sequencing or specific polymerase chain reaction (PCR). Methods: We searched PubMed, EMBASE, and Web of Science from 26 November 2021 to 13 April 2022. This meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and was registered with PROSPERO (CRD42022327894). Three researchers independently extracted data and two researchers assessed quality using pre-specified criteria. The pooled percentage with 95% confidence interval (CI) of asymptomatic infections of SARS-CoV-2 Omicron was estimated using random-effects models. Results: Our meta-analysis included eight eligible studies, covering 7640 Omicron variant-positive individuals with 2190 asymptomatic infections. The pooled percentage of asymptomatic infections was 32.40% (95% CI: 25.30−39.51%) among SARS-CoV-2 Omicron variant-positive individuals, which was higher in the population in developing countries (38.93%; 95% CI: 19.75−58.11%), with vaccine coverage ≥ 80% (35.93%; 95% CI: 25.36−46.51%), with a travel history (40.05%; 95% CI: 7.59−72.51%), community infection (37.97%; 95% CI: 10.07−65.87%), and with a median age < 20 years (43.75%; 95% CI: 38.45−49.05%). Conclusion: In this systematic review and meta-analysis, the pooled percentage of asymptomatic infections was 32.40% among SARS-CoV-2 Omicron variant-positive individuals. The people who were vaccinated, young (median age < 20 years), had a travel history, and were infected outside of a clinical setting (community infection) had higher percentages of asymptomatic infections. Screening is required to prevent clustered epidemics or sustained community transmission caused by asymptomatic infections of Omicron variants, especially for countries and regions that have successfully controlled SARS-CoV-2.

Keywords: COVID-19; Omicron variant; SARS-CoV-2; asymptomatic.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flowchart of the study selection.
Figure 2
Figure 2
The Percentage of Asymptomatic Infections Among SARS-CoV-2 Omicron Variant-Positive Individuals [19,21,32,33,34,41,42,43].
Figure 3
Figure 3
The Percentage of Asymptomatic Infections Among SARS-CoV-2 Omicron Variant-Positive Individuals by Subgroup.
See this image and copyright information in PMC

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References

    1. World Health Organization Coronavirus (COVID-19) Dashboard. 2022. [(accessed on 11 April 2022)]. Available online: https://covid19.who.int/
    1. Wu C., Xu C., Mao F., Xu X., Zhang C. The impact of invisible-spreaders on COVID-19 transmission and work resumption. PLoS ONE. 2022;17:e0252994. doi: 10.1371/journal.pone.0252994. - DOI - PMC - PubMed
    1. Ma Q., Liu J., Liu Q., Kang L., Liu R., Jing W., Wu Y., Liu M. Global percentage of asymptomatic SARS-CoV-2 infections among the tested population and individuals with confirmed COVID-19 diagnosis: A systematic review and meta-analysis. JAMA Netw. Open. 2021;4:e2137257. doi: 10.1001/jamanetworkopen.2021.37257. - DOI - PMC - PubMed
    1. Boyton R.J. Altmann DM. The immunology of asymptomatic SARS-CoV-2 infection: What are the key questions? Nat. Rev. Immunol. 2021;21:762–768. doi: 10.1038/s41577-021-00631-x. - DOI - PMC - PubMed
    1. Vermund S.H., Pitzer V.E. Asymptomatic Transmission and the Infection Fatality Risk for COVID-19: Implications for School Reopening. Clin. Infect. Dis. 2021;72:1493–1496. doi: 10.1093/cid/ciaa855. - DOI - PMC - PubMed

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