CD79A and COVID-19: Our longitudinal study substantially extends prior knowledge by demonstrating: (I) the vast majority (92%) of women with COVID-19 have anti-RBD IgA in their milk; (II) concentrations of anti-RBD IgA increase during the first weeks following onset of symptoms or, if asymptomatic, following the day of diagnostic test; and (III) anti-RBD IgA is present in milk produced by most infected women for at least 2 months.