evidence: As a rule, infants and young children rarely develop severe or enduring cases of COVID-19. And those who do almost invariably suffer from some other serious medical problem. It’s not that kids don’t get infected. They do. More than 90% of kids age 4 and under in the United States test positive for previous or current infection by SARS-CoV-2, the coronavirus that causes this respiratory infection. [...] Possible explanations abound regarding young children’s remarkable resilience to SARS-CoV-2. They seem to harbor fewer receptors for SARS-CoV-2 on their cell surfaces. They’ve had more relatively recent encounters with benign coronaviruses than adults (the latter being less inclined to gum one another’s toys in day care settings or sneeze in each other’s face), bolstering immunity to newcomers.