Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Meta-Analysis
. 2021 Dec 1;4(12):e2137257.
doi: 10.1001/jamanetworkopen.2021.37257.

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

Qiuyue Ma  1 , Jue Liu  1 , Qiao Liu  1 , Liangyu Kang  1 , Runqing Liu  2 , Wenzhan Jing  1 , Yu Wu  1 , Min Liu  1
Affiliations
Meta-Analysis

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

Qiuyue Ma et al. JAMA Netw Open. .

Abstract

Importance: Asymptomatic infections are potential sources of transmission for COVID-19.

Objective: To evaluate the percentage of asymptomatic infections among individuals undergoing testing (tested population) and those with confirmed COVID-19 (confirmed population).

Data sources: PubMed, EMBASE, and ScienceDirect were searched on February 4, 2021.

Study selection: Cross-sectional studies, cohort studies, case series studies, and case series on transmission reporting the number of asymptomatic infections among the tested and confirmed COVID-19 populations that were published in Chinese or English were included.

Data extraction and synthesis: This meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Random-effects models were used to estimate the pooled percentage and its 95% CI. Three researchers performed the data extraction independently.

Main outcomes and measures: The percentage of asymptomatic infections among the tested and confirmed populations.

Results: Ninety-five unique eligible studies were included, covering 29 776 306 individuals undergoing testing. The pooled percentage of asymptomatic infections among the tested population was 0.25% (95% CI, 0.23%-0.27%), which was higher in nursing home residents or staff (4.52% [95% CI, 4.15%-4.89%]), air or cruise travelers (2.02% [95% CI, 1.66%-2.38%]), and pregnant women (2.34% [95% CI, 1.89%-2.78%]). The pooled percentage of asymptomatic infections among the confirmed population was 40.50% (95% CI, 33.50%-47.50%), which was higher in pregnant women (54.11% [95% CI, 39.16%-69.05%]), air or cruise travelers (52.91% [95% CI, 36.08%-69.73%]), and nursing home residents or staff (47.53% [95% CI, 36.36%-58.70%]).

Conclusions and relevance: In this meta-analysis of the percentage of asymptomatic SARS-CoV-2 infections among populations tested for and with confirmed COVID-19, the pooled percentage of asymptomatic infections was 0.25% among the tested population and 40.50% among the confirmed population. The high percentage of asymptomatic infections highlights the potential transmission risk of asymptomatic infections in communities.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest Disclosures: None reported.

Figures

Figure 1.
Figure 1.. Flow Diagram of Study Selection
Figure 2.
Figure 2.. Percentage of Asymptomatic Infections Among the Tested Population by Subgroups
Includes 29 776 306 tested individuals, among whom 11 516 had asymptomatic infections.
Figure 3.
Figure 3.. Percentage of Asymptomatic Infections Among the Confirmed Population by Subgroups
Includes 19 884 individuals with confirmed COVID-19, among whom 11 069 had asymptomatic infections.
Figure 4.
Figure 4.. Funnel Plots Based on the Percentage of Asymptomatic Infections
Includes 29 776 306 tested individuals, among whom 11 516 had asymptomatic infections and 19 884 individuals with confirmed COVID-19, among whom 11 069 had asymptomatic infections. Funnel plot asymmetry indicated possible publication bias.
See this image and copyright information in PMC

References

    1. Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020;395(10223):497-506. doi: 10.1016/S0140-6736(20)30183-5 - DOI - PMC - PubMed
    1. World Health Organization. WHO coronavirus disease (COVID-19) dashboard. Accessed January 28, 2021. https://covid19.who.int/
    1. Kronbichler A, Kresse D, Yoon S, Lee KH, Effenberger M, Shin JI. Asymptomatic patients as a source of COVID-19 infections: a systematic review and meta-analysis. Int J Infect Dis. 2020;98:180-186. doi: 10.1016/j.ijid.2020.06.052 - DOI - PMC - PubMed
    1. World Health Organization. Coronavirus disease (COVID-19): how is it transmitted? December 13, 2020. Accessed January 22, 2021. https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-ho...
    1. Chen C, Zhu C, Yan D, et al. The epidemiological and radiographical characteristics of asymptomatic infections with the novel coronavirus (COVID-19): a systematic review and meta-analysis. Int J Infect Dis. 2021;104:458-464. doi: 10.1016/j.ijid.2021.01.017 - DOI - PMC - PubMed

Publication types