Figure 1.

BNT162b2 vaccinees mount serum anti–RBD–SARS-CoV-2 IgG and IgA, with IgG showing strong neutralization potential. (A) Independent ELISA measurements of anti-RBD IgG and of anti-RBD IgA in serum samples collected from pre-COVID (N = 51), BNT162b2 vaccinees (N = 17), and post-COVID-19 (N = 22) convalescents, as indicated. Convalescent samples were collected within 3–10 weeks post-recovery, as defined by the clinical definition in Israel at time of sample collection. BNT162b2 vaccinee samples for which kinetic samples were available, the value shown represents the peaks of individual responses based on their kinetic curve [see (B) and Table S7 ]. (B) Quantitative kinetic profile of anti-RBD IgG (blue) and IgA (red) in serum sampled (N = 76) in the vaccinee cohort (N = 18), plotted as a function of days, after first vaccine dose. See Table S1 for cohort and sampling details. Independent ordinate axes for IgG (left, blue) and IgA (right, red) highlight the restricted, relative nature of the comparison between isotypes in this experiment, as discussed in the text; see also Figure 2 for subsequent developments. Green arrows indicate timing of the second vaccine dose (the boost). (C) Serum neutralization assessed by SARS-CoV-2 spike-pseudotyped VSV-GFP-ΔG reporter assay on Vero-E6 cells. Neutralization is expressed as a percentage of pseudovirus-infected green cells without serum (total infection = 100%). Percentage of neutralization by sera of pool of four individual vaccinees is plotted as a function of the reciprocal values of sera dilutions displayed on a log2 scale, as indicated (filled circles, total serum, NT50 is reached on average at the dilution of ∼1:360, extrapolated by cross-section with the dashed line. Contribution of IgG to serum neutralization is evaluated by the depletion of the IgG isotype using anti-IgG specific magnetic beads (triangles). See Figure S1F for assessment of completeness and specificity of IgG depletion. Results of three experimental repeats are represented.