The association between plasma IgA anti-SARS-CoV-2 S levels and protection from infection that we and others observed [5], which was not found for IgG anti-SARS-CoV-2 S levels, suggests that circulating IgA is not simply a fractional representation of the IgG responses reflecting the lower frequency of systemic isotype switching to IgA. Here, CD79A is linked to infection.