RESUMEN
COVID-19 course and immunity differ in children and adults. We analyzed immune response dynamics in 28 families up to 12 months after mild or asymptomatic infection. Unlike adults, the initial response is plasmablast-driven in children. Four months after infection, children showed an enhanced specific antibody response and a lower but detectable S1-specific B and T cell response compared to their parents. While specific antibodies declined, neutralizing antibody activity and breadth increased in both groups. Frequencies of S1-specific B and T cell responses remained stable. However, progressive maturation of the S1 specific immune response was observed in children one year after infection with IgA class switch and expression of CD27 on B cells and T cell maturation. Hence, the immune response in children persists over 12 months, but dynamically changes in quality, with progressive neutralizing, breadth, and memory maturation. This implies a benefit for booster vaccination in children to consolidate memory formation.