CD40LG and COVID-19: However, future investigations in large longitudinal cohorts of SARS-CoV-2-naïve and COVID-19-recovered children receiving the BNT vaccine, with the inclusion of more RBD of the SARS-CoV-2 variants circulating in Ethiopia and two more immunoglobulin classes (IgM and IgG) are needed for a better understanding of the kinetics, breadth, and durability of vaccine-, natural infection- or both (hybrid)-induced humoral immunity in children.