Susceptibility to and transmission of COVID-19 amongst children and adolescents compared with adults: a systematic review and meta-analysis

Background The degree to which children and young people are infected by and transmit the SARS-CoV-2 virus is unclear. Clinical series and testing cohorts based upon screening of symptomatic cases provide biased estimates of susceptibility in children. The role of children and young people in transmission of SARS-CoV-2 is dependent on susceptibility, symptoms, viral load, social contact patterns and behaviour. Methods We undertook a rapid systematic review of contact-tracing studies and population-screening studies to address the question What is the susceptibility to and transmission of SARS-CoV-2 by children and adolescents compared with adults? We searched PubMed and medRxiv on 16 May 2020 and identified 6327 studies, with additional studies identified through handsearching of cited references (2) and professional contacts (4). We assessed quality, summarized findings and undertook a random effects meta-analysis of contact-tracing studies. Results 18 studies met inclusion criteria; 9 contact-tracing, 8 population-screening and 1 systematic-review. Meta-analysis of contact tracing studies showed that the pooled odds ratio of being an infected contact in children compared with adults for all contact tracing studies was 0.44 (0.29, 0.69) with substantial heterogeneity (63%). Findings from a systematic review of household clusters of COVID-19 found 3/31 (10%) were due to a child index case and a population-based school contact tracing study found minimal transmission by child or teacher index cases. Findings from population-screening studies were heterogenous and not suitable for meta-analysis. Large studies from Iceland, the Netherlands and Spain and an Italian municipal study showed markedly lower SARS-CoV-2 prevalence amongst children and young people, however studies from Stockholm, England and municipalities in Switzerland and Germany showed showed no difference in infection prevalence between adults and children. Conclusions There is preliminary evidence that children and young people have lower susceptibility to SARS-CoV-2, with a 56% lower odds of being an infected contact. There is weak evidence that children and young people play a lesser role in transmission of SARS-CoV-2 at a population level. Our study provides no information on the infectivity of children