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

•Household settings related to a higher asymptomatic SARS-CoV-2 transmission risk•Lower transmission potential for asymptomatic than (pre)symptomatic infections•Asymptomatic transmission rate lower in China than other countries included Global evidence on the transmission of asymptomatic SARS-CoV-2 infection needs to be synthesized. 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. 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