Alliance for Pandemic Preparedness

October 9, 2020

What Do We Know about SARS-CoV-2 Transmission? A Systematic Review and Meta-Analysis of the Secondary Attack Rate and Associated Risk Factors

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  • A systematic review and meta-analysis of the secondary attack rate (SAR) of SARS-Cov-2 in household and healthcare settings indicated that the SAR among symptomatic people was higher than that for asymptomatic people (RR=3.2). The SAR is the proportion of contacts of a SARS-CoV-2 case who subsequently became infected. Adults showed higher susceptibility to infection than children (RR=1.7), and spouses of index cases were more likely to be infected compared to other household contacts (RR=2.4). In healthcare settings, the pooled SAR was estimated at 0.7%, while the pooled household SAR was estimated at 18%. The authors suggest that these results indicate a need to account for setting-specific transmission risk, and that individuals with confirmed infection should be isolated away from other household members when possible.

Koh et al. (Oct 8, 2020). What Do We Know about SARS-CoV-2 Transmission? A Systematic Review and Meta-Analysis of the Secondary Attack Rate and Associated Risk Factors. PLOS ONE. https://doi.org/10.1371/journal.pone.0240205