Figure 1.

Anti‐tetanus, diphtheria and acellular pertussis (Tdap) antibody concentrations in mothers and their infants from Tdap‐vaccinated and ‐unvaccinated pregnancies (a–e). The proportion of infants from Tdap‐vaccinated and ‐unvaccinated pregnancies reaching antibody thresholds (f–j). (a–e) Anti‐Tdap immunoglobulin (Ig)G were quantified in mother–infant pairs from vaccinated (white circle) and unvaccinated (black circle) pregnancies. Data were log‐transformed, and a random‐effects model applied. Mean and 95% confidence intervals are shown. The vaccinated group had significantly elevated antibodies to (a) PTx, (b) FHA, (c) Prn, (d) Dtx and (e) TTx vaccine antigens in mothers at birth, in cord blood and in the infant prevaccination (pre‐vac; 7 weeks of age). Post‐infant vaccination (post‐vac; 5 months of age), there were no significant differences in antibody to any of the vaccine antigens between vaccinated and unvaccinated groups (*P < 0·05; ***P < 0·001; ****P < 0·0001; unvaccinated n = 15; vaccinated n = 16). (f–j) Cut‐offs were set at ≥20 IU/ml for pertussis antigens and ≥0·1 IU/ml for DTx and TTx. The proportion of infants at birth, 7 weeks and 5 months that reached these cut‐offs is represented as a percentage of total samples analysed in vaccinated (solid line) and unvaccinated (dashed line) groups. At birth and 7 weeks, the percentage of infants reaching seropositive levels for PTx, FHA, Prn and DTx was significantly higher in the group born to Tdap‐vaccinated mothers than those born to non‐vaccinated mothers. There was no difference for TTx. Post‐primary immunization, there was no difference between the two groups (**P < 0·01; ***P < 0·001; ****P < 0·0001).