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Infectious Medicine 2023, 2(1): 11-18 https://doi.org/10.1016/j.imj.2022.12.001
Original Article | Open Access | Issue | Published: 17 December 2022

Transmission risk of asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis

Show Author's Information Ci Zhangab1,  Chao Zhouc1,  Wanqing Xud,  Shimin Zhenge,  Yanxiao Gaof,  Peiqi Lig,  Luojia Dengc,  Xuezhixing Zhangh,  Qianxue Jiangc,  Frank Qiani,  Xianhong Liab,  Honghong Wangab,  Huachun Zouf,  Yinglin Xiaj,  Tao Wangc,  Hui Luc,  Han-Zhu Qianh#( )
Xiangya School of Nursing, Central South University, Changsha, China
Xiangya Center for Evidence-Based Nursing Practice & Healthcare Innovation (A JBI Affiliated Group), Changsha, Hunan Province, China
Department of Bioinformatics and Biostatistics, Shanghai Jiao Tong University, Shanghai, China
T.H. Chan School of Public Health, Harvard University, Boston, MA, USA
Department of Biostatistics and Epidemiology, East Tennessee State University, Johnson City, TN, USA
School of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, China
School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
School of Public Health, Yale University, New Haven, CT, USA
Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA

1 These authors contributed equally to this work.

Keywords:
Meta-analysis, Systematic review, SARS-CoV-2, Asymptomatic, Transmission rate
Cite this article:
Zhang C, Zhou C, Xu W, et al. Transmission risk of asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis. Infectious Medicine, 2023, 2(1): 11-18. https://doi.org/10.1016/j.imj.2022.12.001
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Abstract Full text About this article
Background

Global evidence on the transmission of asymptomatic SARS-CoV-2 infection needs to be synthesized.

Methods

A search of 4 electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science databases) as of January 24, 2021 was performed. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Studies which reported the transmission rate among close contacts with asymptomatic SARS-CoV-2 cases were included, and transmission activities occurred were considered. The transmission rates were pooled by zero-inflated beta distribution. The risk ratios (RRs) were calculated using random-effects models.

Results

Of 4923 records retrieved and reviewed, 15 studies including 3917 close contacts with asymptomatic indexes were eligible. The pooled transmission rates were 1.79 per 100 person-days (or 1.79%, 95% confidence interval [CI] 0.41%–3.16%) by asymptomatic index, which is significantly lower than by presymptomatic (5.02%, 95% CI 2.37%–7.66%; p < 0.001), and by symptomatic (5.27%, 95% CI 2.40%–8.15%; p < 0.001). Subgroup analyses showed that the household transmission rate of asymptomatic index was (4.22%, 95% CI 0.91%–7.52%), four times significantly higher than non-household transmission (1.03%, 95% CI 0.73%–1.33%; p=0.03), and the asymptomatic transmission rate in China (1.82%, 95% CI 0.11%–3.53%) was lower than in other countries (2.22%, 95% CI 0.67%–3.77%; p=0.01).

Conclusions

People with asymptomatic SARS-CoV-2 infection are at risk of transmitting the virus to their close contacts, particularly in household settings. The transmission potential of asymptomatic infection is lower than symptomatic and presymptomatic infections. This meta-analysis provides evidence for predicting the epidemic trend and promulgating vaccination and other control measures. Registered with PROSPERO International Prospective Register of Systematic Reviews, CRD42021269446; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=269446.


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Abstract
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About this article

Transmission risk of asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis

Show Author's information Ci Zhangab1, Chao Zhouc1, Wanqing Xud, Shimin Zhenge, Yanxiao Gaof, Peiqi Lig, Luojia Dengc, Xuezhixing Zhangh, Qianxue Jiangc, Frank Qiani, Xianhong Liab, Honghong Wangab, Huachun Zouf, Yinglin Xiaj, Tao Wangc, Hui Luc, Han-Zhu Qianh#( )
Xiangya School of Nursing, Central South University, Changsha, China
Xiangya Center for Evidence-Based Nursing Practice & Healthcare Innovation (A JBI Affiliated Group), Changsha, Hunan Province, China
Department of Bioinformatics and Biostatistics, Shanghai Jiao Tong University, Shanghai, China
T.H. Chan School of Public Health, Harvard University, Boston, MA, USA
Department of Biostatistics and Epidemiology, East Tennessee State University, Johnson City, TN, USA
School of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, China
School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
School of Public Health, Yale University, New Haven, CT, USA
Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA

1 These authors contributed equally to this work.

Abstract

Background

Global evidence on the transmission of asymptomatic SARS-CoV-2 infection needs to be synthesized.

Methods

A search of 4 electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science databases) as of January 24, 2021 was performed. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Studies which reported the transmission rate among close contacts with asymptomatic SARS-CoV-2 cases were included, and transmission activities occurred were considered. The transmission rates were pooled by zero-inflated beta distribution. The risk ratios (RRs) were calculated using random-effects models.

Results

Of 4923 records retrieved and reviewed, 15 studies including 3917 close contacts with asymptomatic indexes were eligible. The pooled transmission rates were 1.79 per 100 person-days (or 1.79%, 95% confidence interval [CI] 0.41%–3.16%) by asymptomatic index, which is significantly lower than by presymptomatic (5.02%, 95% CI 2.37%–7.66%; p < 0.001), and by symptomatic (5.27%, 95% CI 2.40%–8.15%; p < 0.001). Subgroup analyses showed that the household transmission rate of asymptomatic index was (4.22%, 95% CI 0.91%–7.52%), four times significantly higher than non-household transmission (1.03%, 95% CI 0.73%–1.33%; p=0.03), and the asymptomatic transmission rate in China (1.82%, 95% CI 0.11%–3.53%) was lower than in other countries (2.22%, 95% CI 0.67%–3.77%; p=0.01).

Conclusions

People with asymptomatic SARS-CoV-2 infection are at risk of transmitting the virus to their close contacts, particularly in household settings. The transmission potential of asymptomatic infection is lower than symptomatic and presymptomatic infections. This meta-analysis provides evidence for predicting the epidemic trend and promulgating vaccination and other control measures. Registered with PROSPERO International Prospective Register of Systematic Reviews, CRD42021269446; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=269446.

Keywords: Meta-analysis, Systematic review, SARS-CoV-2, Asymptomatic, Transmission rate

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Publication history

Received: 05 October 2022
Revised: 24 November 2022
Accepted: 03 December 2022
Published: 17 December 2022
Issue date: March 2023

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© 2022 The Author(s). Published by Elsevier Ltd on behalf of Tsinghua University Press.

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This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

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