Excerpted from abstract
We run searches in PubMed, medRxiv and WHO COVID-19 database to identify relevant studies reporting on the COVID-19 transmission routes among infected (both symptomatic and asymptomatic) children and adolescences. This update covers the period up to 4 May 2020. The literature screening was shared between four reviewers (XL, WX, YH, AK). Each new title, abstract and full text was screened by one reviewer. A total of 993 publications were retrieved (130 unique from the original search; 201 unique from the first update and 662 from the second update). A total of 80 unique studies were included: 2 studies (1, 64) investigating SARS-COV-2 transmission from diagnosed children; 6 studies presenting direct or indirect evidence on the potential of COVID transmission by children (2, 65-69); 73 studies (3-64, 70-81) exploring the transmission routes of how children were infected including 2 studies/ reports exploring school outbreaks (64, 81). We found 32 reviews (89- 120) exploring the transmission of COVID-19 infection among children and 1 policy brief from the Swiss National Science Task Force (82). References of previous reviews and briefs were searched by four reviewers (YH, WX, XL, ET). We also found five studies (83-87), that addressed a relevant research question (i.e proportion of children infected identified through random or targeted population testing) and we also report results from a large hospital based study from the UK (88) and a nation- wide case-series from China (121). We have included these studies, but we plan to expand the scope of our review to systematically search for this and other relevant research questions (including studies on attack rate of the disease in children and modelling studies on the effect of school closures).