Evolution of the anti-RBD antibody response over time in repeat CCP donors. The time from onset of symptoms (33-114 days) was divided in quartiles containing similar numbers (between 19 and 22) of samples obtained from the donors shown in Figure 1. The mean and median OD_450nm were calculated using all samples in each quartile. Each sample is represented by a dot. Boxes and horizontal bars denote IQR, whereas horizontal line and lozenge in boxes correspond to median and mean value, respectively. Whisker end points are equal to the maximum and minimum values below or above the median ± 1.5 times the IQR. Statistical significance was noted as not significant (NS). *P < .05; **P < .01; and ***P < .001.