CD79A and infection: Spike-specific IgA levels were eighteen-fold higher in nasal secretions from participants with prior infection as compared to SARS-CoV-2 infection naïve participants (median 46.0 vs. 2.5 AU/mL, p<0.001), while corresponding difference was only three-fold in saliva (13.8 vs. 4.2 AU/mL, p<0.01) and two-fold in serum (14 400 vs. 7 300 AU/mL) from the same individuals (Figures 4A–C).