ACE2 and infection: Children may have lower susceptibility to severe infection due to age-related immune differences (5), including pre-existing immunity from more frequent infection with other human coronaviruses (6–8); naïve immune responses that favor broad reactivity (9); lower rates of proinflammatory cytokine imbalances and related comorbidities (10); and reduced viral entry in the lungs, perhaps owing to more limited angiotensin converting enzyme 2 (ACE2) cell receptor expression or binding (10, 11).