The presence of SARS-CoV-2-specific IgA and IgG in bilateral liquid colostrum of two pre-COVID-19 controls, and the left breast of a third control (participant 19), suggests a prior infection that elicited a humoral response that cross-reacted with SARS-CoV-2-RBD (Supplementary Fig. S1A). This evidence concerns the gene CD79A and infection.