CD79A and COVID-19: Compared to the “no prior COVID-19” subjects post-dose 2, both mucosal S-IgG and S-IgA titres were higher (4.0 and 1.7-fold, p = 0.001 and p = 0.008, respectively) in the “prior COVID-19” group after a single Sputnik-V dose (Fig. 4D,E).