Figure 4.

Baseline fold changes in SARS-CoV-2 IgG-S reactivity upon COVID-19 vaccination. The baseline fold changes of IgG antibody titers to SARS-CoV-2 spike receptor-binding domain (IgG-S) were analyzed in serum samples from subjects with seronegative and seropositive status at baseline at distinct timepoints: after first (D28) and second (D28*) doses, including subjects receiving a half dose (ChAd Half Dose), n = 208, 189 and 294, 254, respectively), represented by light blue symbols on the right side of each graph, as compared to the reference volunteers receiving the standard-dose (ChAd Full Dose), n = 90, 87 and 45, 44, respectively), represented by dark blue symbols on the left side of each graph in relation to the levels observed prior vaccination (D0). The levels of IgG-S were determined by the chemiluminescent microparticle immunoassay and the baseline fold changes were calculated as described in the Methods. The changes in IgG-S reactivity were assessed defining the fold-change = 1 as the reference for unaltered levels (dashed line). Data are presented as a scatter plot of baseline fold-changes in IgG-S titers at D28 and D28* according to the individual baseline values observed at D0 (D28/D0 and D28*/D0) over bars representing the median fold changes. Comparative analyses of baseline fold changes in IgG-S titers were performed by Mann-Whitney test. Significant differences were considered at p ≤ 0.05 (* represents the p value power; * p≤0.05, **p≤0.01, *** p≤0.001, **** p≤0.0001) and are indicated by connecting lines and # symbol for intragroup (D28 vs D28*) and intergroup ChAd Full Dose vs ChAd Half Dose comparisons, respectively.