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Estimating the Extent of True Asymptomatic COVID-19 and Its Potential for Community Transmission: Systematic Review and Meta-Analysis

22 Pages Posted: 4 Jun 2020

See all articles by Oyungerel Byambasuren

Oyungerel Byambasuren

Bond University - Institute for Evidence-Based Healthcare

Magnolia Cardona

Bond University - Institute for Evidence-Based Healthcare

Katy Bell

University of Sydney - School of Public Health

Justin Clark

Bond University - Institute for Evidence-Based Healthcare

Mary-Louise McLaws

University of New South Wales (UNSW) - School of Public Health and Community Medicine

Paul Glasziou

Bond University - Institute for Evidence-Based Healthcare

More...

Abstract

Background: The prevalence of true asymptomatic COVID-19 cases is critical to policy makers considering the effectiveness of mitigation measures against the SARS-CoV-2 pandemic. We aimed to synthesise all available research on the asymptomatic rates.

Methods: We searched PubMed, Embase, Cochrane COVID 19 trials, and European PMC for pre-print platforms such as MedRxiv, Research Square, and F1000 Research. We included primary studies reporting on asymptomatic prevalence where: (a) the sample frame was not contingent on the presence or absence of symptoms, and (b) there was sufficiently long follow up to identify pre-symptomatic cases. Meta-analysis used fixed effect and random effects models.

Results: We screened 571 articles and included five studies from three countries (China (2), USA (2), Italy (1)) that include 599 COVID-19 cases and 9,297 contacts. Diagnosis in all studies was confirmed using a RT-PCR test. The proportion of asymptomatic cases ranged from 6% to 41%. Meta-analysis (fixed effect) found that the proportion of asymptomatic cases was 16% (95% CI: 12% - 20%) overall; higher in non-aged care 19% (15% - 24%), and lower in long-term aged care 8% (4% - 14%). Two studies provided direct evidence of forward transmission of the infection by asymptomatic cases, but suggested lower rates than symptomatic cases.

Conclusion: Our meta-analytic estimates of the prevalence of asymptomatic COVID-19 cases are lower than many highly publicized studies, but still substantial. Further robust epidemiological evidence is urgently needed, including in sub-populations such as children, to better understand the importance of asymptomatic cases for driving spread of the pandemic.

Funding Statement: OB is supported by NHMRC Grant APP1106452. PG is supported by NHMRC Australian Fellowship grant 1080042. KB was supported by NHMRC Fellowship grant 1174523 and Program grant 1113532. There was no funding source for this study.

Declaration of Interests: Prof Mary-Louise McLaws is a member of World Health Organization Health Emergencies Program Experts Advisory Panel for Infection Prevention and Control Preparedness, Readiness and Response to COVID-19. All other authors declare no competing interests.

Keywords: CORONAVIRUS; COVID19; SARS-CoV-2; Asymptomatics; prevalence; Transmission; systematic review; meta-analysis

Suggested Citation

Byambasuren, Oyungerel and Cardona, Magnolia and Bell, Katy and Clark, Justin and McLaws, Mary-Louise and Glasziou, Paul, Estimating the Extent of True Asymptomatic COVID-19 and Its Potential for Community Transmission: Systematic Review and Meta-Analysis (4/23/2020). Available at SSRN: https://ssrn.com/abstract=3586675 or http://dx.doi.org/10.2139/ssrn.3586675

Oyungerel Byambasuren (Contact Author)

Bond University - Institute for Evidence-Based Healthcare ( email )

14 University Dr
Robina, QLD 4226
Australia
61 7 5595 1855 (Phone)

Magnolia Cardona

Bond University - Institute for Evidence-Based Healthcare

14 University Dr
Robina, QLD 4226
Australia

Katy Bell

University of Sydney - School of Public Health

University of Sydney
Sydney, NSW 2006
Australia

Justin Clark

Bond University - Institute for Evidence-Based Healthcare

14 University Dr
Robina, QLD 4226
Australia

Mary-Louise McLaws

University of New South Wales (UNSW) - School of Public Health and Community Medicine

Kensington
High St
Sydney, NSW 2052
Australia

Paul Glasziou

Bond University - Institute for Evidence-Based Healthcare

14 University Dr
Robina, QLD 4226
Australia

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