Estimating the extent of asymptomatic covid-19 and its potential for community transmission: Systematic review and meta-analysis
Canadian Journal of Infection Control
; 36(1):30-38, 2021.
Article
in English
| EMBASE | ID: covidwho-2239457
ABSTRACT
Background:
Knowing the prevalence of true asymptomatic coronavirus disease 2019 (COVID-19) cases is critical for designing mitigation measures against the pandemic. We aimed to synthesize all available research on asymptomatic cases and transmission rates.Methods:
We searched PubMed, Embase, Cochrane COVID-19 trials, and Europe PMC for primary studies on asymptomatic prevalence in which (1) the sample frame includes at-risk populations, and;(2) follow-up was sufficient to identify pre-symptomatic cases. Meta-analysis used fixed-effects and random-effects models. We assessed risk of bias by combination of questions adapted from risk of bias tools for prevalence and diagnostic accuracy studies.Results:
We screened 2,454 articles and included 13 low risk-of-bias studies from seven countries that tested 21,708 at-risk people, of which 663 were positive and 111 asymptomatic. Diagnosis in all studies was confirmed using a real-time reverse transcriptase–polymerase chain reaction test. The asymptomatic proportion ranged from 4% to 41%. Meta-analysis (fixed effects) found that the proportion of asymptomatic cases was 17% (95% CI 14% to 20%) overall and higher in aged care (20%;95% CI 14% to 27%) than in non-aged care (16%;95% CI 13% to 20%). The relative risk (RR) of asymptomatic transmission was 42% lower than that for symptomatic transmission (combined RR 0.58;95% CI 0.34 to 0.99, p = 0.047).Conclusions:
Our one-in-six estimate of the prevalence of asymptomatic COVID-19 cases and asymptomatic transmission rates is lower than those of many highly publicized studies but still sufficient to warrant policy attention. Further robust epidemiological evidence is urgently needed, including in subpopulations such as children, to better understand how asymptomatic cases contribute to the pandemic.
article; asymptomatic coronavirus disease 2019; asymptomatic transmission; attention; child; community transmission; controlled study; diagnostic accuracy; diagnostic test accuracy study; disease re-emergence; Embase; Europe; evidence based medicine; female; follow up; human; male; Medline; meta analysis; pandemic; prevalence; public health; real time reverse transcription polymerase chain reaction; risk assessment; risk factor; systematic review
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Collection:
Databases of international organizations
Database:
EMBASE
Type of study:
Reviews
/
Systematic review/Meta Analysis
Language:
English
Journal:
Canadian Journal of Infection Control
Year:
2021
Document Type:
Article
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