IGHG3 and infection: Similar to natural infections, IgG3 was the major virus-binding IgG subclass generated following MV-CHIK vaccination (median IgG3 titers at 1 month for P and P+B were 626 [IQR 287–1068] and 1146 [IQR 900–1818], respectively), and this trend persisted even at 6 months (Figure 3A and Supplemental Figure 2).