Longitudinal Analysis of Humoral and Cellular Immunity in SARS-CoV-2 Exposed Families

Identification of previous SARS-CoV-2 infection typically relies on serology, yet T cells play a key role in the adaptive immune response against SARS-CoV-2. Here, we investigated in parallel the SARS-CoV-2 specific humoral and cellular responses as well as endemic human coronavirus specific humoral and cross-reactive cellular responses in a family cohort comprising 164 children and 235 adults at 3-4 and 11-12 months after contact with SARS-CoV-2 . While the majority of adults had a combined serological and T cell response, relatively more children showed a T cell response only than a combined response. The magnitude of the T cell response was significantly correlated with symptoms and the humoral response. Moreover, SARS-CoV-2 infection significantly boosted endemic coronavirus specific cellular response. Overall our data suggest discordant humoral and cellular responses, reflecting either sensitization or mild infection with rapid viral clearance. Consequently, limiting epidemiologic analysis to SARS-CoV-2 antibodies may underestimate infection rates in children.