In an attempt to understand the longevity of the humoral immune response induced by both natural infection and by the different vaccines, we have been carrying out a prospective study of the kinetics of IgG and IgM antibodies specific for SARS-CoV-2 by longitudinal follow-up of individuals with documented past COVID-19 (naturally immunized, NI) since August 2020, and of vaccinated individuals since January 2021. Here, CD40LG is linked to infection.