Figure 4.

SARS-CoV-2 RBD-specific IgA reactivity of groups of individuals with the indicated infection/vaccination record determined by the FCCA. (A) The variant-wise comparison of median SARS-CoV-2 anti-RBD IgA antibodies (1:100) across 11 study cohorts, including a non-exposed group. Squares represent convalescent and/or vaccinated groups while circles show exclusively vaccinated groups. The median time, in days, since the last infection ± vaccination is indicated on the right of each graph in the color of the indicated group. (B) The above information represented in cohort-wise violin plots in the color of the indicated group. Horizontal black lines indicate the median while dotted lines show the upper and lower quartiles. IgA reactivities are displayed as log₁₀(∆gMFI-PE). Area indicating FCCA threshold is shaded in grey, denoting negative values. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001 as determined by the Friedman test with Dunn’s multiple comparison correction. In (A), the statistic is performed without the non-exposed group.