Fig. 3.

Anti-SARS-CoV-2 IgG concentration according to time since onset of symptoms.

Graphs show the concentration of SARS-CoV-2 antibody against (a) spike (S), (b) receptor binding domain (RBD) and (c) nucleocapsid (N) in arbitrary units (AU) (based on the calibrated internal standard serum) of the COVID-19 cohort split in to intervals of 0−7 days, 8–14 days, 15–21 days and over 21 (>21) days since symptom onset (to sample collection). Error bars show geometric mean with 95 % CI, line shows positive/negative discrimination cut-off, *p < 0.05, ** p < 0.01 determined by Dunn’s multiple comparisons test. Comparisons across interval groups had p < 0.0001 by one-way ANOVA Kruskal-Wallis test. The assay sensitivity at each time point is shown in Table 3.