Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study – The Lancet Infectious Diseases

study in Wuhan of around 27K households with around 29K primary covid cases & 27K contacts found that children and adolescents (<20y) were one and a half times more likely to be infectious to others than adults>60y. They had higher infectivity than those aged 20-39 & 40-59.

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30981-6/fulltext