Fig. 2

SARS-CoV-2 IgG (S-RBD) and neutralizing activity kinetics. A Antibodies to the receptor-binding domain of the S1 subunit of the viral spike protein [IgG (S-RBD)] and neutralizing activity against (B) wild-type virus, (C) Delta variant, and (D) Omicron variants in sera were determined in infection-naïve participants who provided peripheral blood samples for serological assays at five time points during 48 weeks after receiving the first vaccine dose: at baseline (before the first vaccine dose) and at 8 weeks (period 1), 12 weeks (period 2), 24 weeks (period 3), and 48 weeks (period 4) after the first dose. Between 24 (period 3) and 48 weeks (period 4) after the first dose, booster vaccination with BNT162b2 or mRNA-1273 was completed. Period 4 was approximately 3 months after the booster vaccination. The participants were stratified into three subgroups: healthcare workers, outpatients, and residents of long-term care facilities. Each dot represents an individual participant. The boxes span the interquartile range; the line within each box denotes the median, and the whiskers are the largest and smallest values within the range of ± 1.5-fold in the interquartile range from the first and third quartile. The dashed line in panel A indicates a cut-off of 50 AU/mL for assay positivity, whereas those in panels B–D indicate the cut-off of 30% for assay positivity, as determined previously. The gray areas in panels A–D represent negative results. The numbers above each column indicate the number of participants with positive/negative assay results and the proportion of participants with positive assay results. Fold-comparison in geometric mean IgG (S-RBD) levels relative to that in healthcare workers in period 1 is shown as a number with the “ × ” symbol in panel A. Fold-comparison in median neutralizing activity relative to that against the wild-type virus in healthcare workers in period 1 is shown as a number with the “ × ” symbol in panels B–D. P-values are indicated above each plot. HW; healthcare workers, OP; outpatients, LTCFs; residents of long-term care facilities