What is Known:

• COVID-19 infection is generally mild or asymptomatic in children and adolescents.

• Belgian strategy of testing was focused on symptoms.

• Adults are believed to be responsible for most of familial clusters.

What is New:

• Serological testing gives a more accurate view of the rate of infected children.

• Based on serological results, children have been infected as frequently as adults during the first and second wave in Belgium.

• Seventy-five percent of SARS-CoV-2 IgG-positive children presented a mild symptomatology, and 25% were totally asymptomatic.

• Children could represent the source of infection within household.