Le Polain said that large serology studies — in which researchers collect blood samples from a cross-section of people to get a better sense of how deeply the virus has penetrated the population of a city, a region, a country — should help shed light on how likely children are to be infected in the first place.

An early look, from Geneva, suggests when we’re talking about children we need to distinguish between young children on the one hand and tweens and teens on the other. Published last week in the journal The Lancet, the study found very little evidence of prior Covid-19 infection among children ages 5 to 9 years (the youngest included). But children ages 10 to 19 were as likely to have antibodies to the infection as adults ages 20 to 49 — and more likely than adults older than that.

One thing that is clear is that the disease is generally far less severe for children than it can be for older adults. Deaths among children have been few and the percentage of children who need hospitalization for the illness is substantially lower than it is among adults.