CD79A and COVID-19: In another recent study, variation in the SARS-CoV-2 IgG and IgA responses in COVID-19 mRNA-vaccinated or infected pregnant and lactating women was higher in the milk than in the serum.29 Although antibodies were only tested against the RBD, the study by Collier et al., along with our recent profiling studies in COVID-19 patient sera, indicate that the mucosal response to SARS-CoV-2 in breast milk may be more variable than the systemic response measured in serum.27