To investigate the relative contribution of IgG and IgA to the viral neutralization activity of immune sera, we selectively depleted IgG, IgA, or both by passing sera from five vaccinees with a recent Omicron infection through protein G or peptide M columns, and measured neutralization of the RBD wt, Delta, BA.1, and BA.2 (Figure 5F). Here, CD79A is linked to infection.