Fig. 3

IgM and IgA antibody isotype responses to SARS-CoV-2 after immunization. A, B Multiplex bead-based antibody binding assay that measures the IgM (A) or IgA-specific (B) antibody response to 4 SARS-CoV-2 viral antigens (S1, S2, RBD, and NP). Median Fluorescent Intensity (MFI) is shown and background well subtraction has been used to remove the nonspecific signal. Each dot represents an individual at baseline before vaccine (week 0), 3 weeks after the first dose of BNT162b2 COVID-19 vaccine (week 3) or 4 weeks after the second dose of BNT162b2 COVID-19 vaccine (week 7). Bars represent the group median. The number of individuals in each group are shown below the graphs in Fig. 1. Individuals with a previous history of SARS-CoV-2 infection (seropositive; blue), no previous history of infection (seronegative; red), and individuals with possible undiagnosed infection (green). The dashed line indicates a threshold determined by the sum of the mean and standard deviation for the negative control (beads without antigen). Statistical tests for significant differences between groups were unpaired, two-tailed Wilcoxon-Mann-Whitney test with a significant threshold of P < 0.05