Fig. 3.

Neonatal concentrations of anti-S (a) IgG antibodies did not differ in relation to maternal third trimester immunization timing (P = 0.80). Anti-RBD-specific (b) IgG concentrations in neonatal sera were positively correlated with increasing time since vaccination (r =  0.26; P = 0.001). Placental transfer ratios of anti-S (c) and anti-RBD-specific (d) IgG were directly associated with longer duration since immunization (r =  0.49; P  < 0.001 and r= 0.83; P  < 0.001, respectively). Correlations, as well as correspondent R and P values were calculated by Pearson's test, as shown in each panel. The dotted lines are the 95% confidence intervals.