Development and persistence of memory immune recall response following SARS-CoV-2 infection in children.

SARS-CoV-2 infection is generally mild in children, yet the magnitude and durability of post-infection immune memory remain poorly defined. In this longitudinal study, humoral and cellular immune responses were comprehensively analyzed in 10 SARS-CoV-2-infected children followed for 12 months. Antigen-specific B and T cells were stimulated ex vivo to assess their frequency, persistence, phenotype, and magnitude of recall responses. Natural infection induced robust and long-lasting antigen-specific memory CD4+ T cells that proliferated upon reactivation, exhibited protective Th1 and Th17 polarization, and promoted IgG and IgA class switching in memory B cells, priming them for neutralizing antibody secretion. In parallel, infection generated durable memory CD8+ T cells that expanded upon reactivation and retained cytotoxic capacity, as indicated by sustained granzyme and perforin expression. Together, these results indicate that SARS-CoV-2 infection in children elicits a robust, coordinated, and durable humoral and cellular immune memory that may underlie long-term protective immunity.