Fig. 2: Analysis of the antibody response profile at the time of first vaccination (T0), second vaccination (T1), and 3 weeks after (T2) in subjects infected during the first (orange dots) and the second (red dots) COVID-19 wave.

Median values with the interquartile range are displayed; the horizontal dot lines indicate cutoff value to discriminate positive and negative samples for each assay, according to the manufacturer’s instructions. a IgG for the SARS-CoV-2 nucleocapsid protein N (sample sizes: T0, T1, and T2 n = 25, for P.I. first wave, T0 and T1 n = 26, T2 n = 24 for P.I. second wave); b IgM for the spike glycoprotein (sample sizes: T0, T1, and T2 n = 25, for P.I. first wave, T0 and T1 n = 26, T2 n = 24 for P.I. second wave); c IgA for the spike glycoprotein (sample sizes: T0, T1, and T2 n = 25, for P.I. first wave, T0 and T1 n = 26, T2 n = 24 for P.I. second wave); d IgG for the receptor-binding domain (RBD) of the spike (sample sizes: T0, T1, and T2 n = 25, for P.I. first wave, T0 and T1 n = 26, T2 n = 24 for P.I. second wave); e neutralization assay, expressed as infectious dose (ID50) (sample sizes: T0, T1, and T2 n = 25, for P.I. first wave, T0 and T1 n = 26, T2 n = 25 for P.I. second wave). P values were calculated using the nonparametric two-tailed Wilcoxon matched-pairs signed-rank test for within-group comparisons (bars on top) and the nonparametric Kruskal–Wallis test for between-groups comparisons (bars on bottom). Differences were considered significant if p < 0.05.