Levels of antibodies specific to diphtheria toxoid, tetanus toxoid, and Haemophilus influenzae type b in healthy children born to Tdap-vaccinated mothers.
Introduction: Vaccination of pregnant women protects both women and their newborns against some infectious diseases. Thailand implemented tetanus toxoid (TT) vaccination of pregnant women in 1977, which was replaced by tetanus-diphtheria toxoid (dT) vaccination in 2005. The tetanus-diphtheria-acellular pertussis (Tdap) vaccine has been recommended for pregnant women at 27-36 weeks of gestation since 2012 in several countries. Data on antibody responses to diphtheria toxoid (DT), TT, and Hemophilus influenzae type b (Hib) induced by combined vaccines in children born to TT-vaccinated and/or Tdap-vaccinated mothers are limited. Material and
Methods: We investigated anti-DT, anti-TT, and anti-Hib IgG responses in a cohort of Thai children (ClinicalTrial.gov NCT02408926) born to mothers who received a TT-containing and/or the Tdap vaccine during pregnancy. Children born to Tdap-vaccinated mothers were randomized to receive either a hexavalent (Infanrix-hexa) or pentavalent (Quinvaxem) vaccine, whereas children born to TT-vaccinated mothers received only Quinvaxem vaccine at 2, 4, 6, and 18 months of age. IgG levels were evaluated at birth (cord blood), 2 (pre-primary), 7 (post-primary), 18 (pre-booster), and 19 months of age (post-booster) using a commercially available enzyme-linked immunoassay.
Results: Seroprotective concentrations of anti-DT, anti-TT, and anti-Hib IgG were achieved in >90% and >99% of children following primary and booster vaccination, respectively. Among children born to Tdap-vaccinated mothers, the pentavalent vaccine induced higher levels of anti-Hib IgG than the hexavalent vaccine after primary and booster vaccination. Significantly higher anti-Hib IgG levels were observed among children receiving the pentavalent vaccine and who were born to TT-vaccinated mothers than among children receiving the pentavalent vaccine and born to Tdap-vaccinated mothers after primary and booster vaccination.
Conclusions: Vaccination with a TT-containing and/or the Tdap vaccine during pregnancy did not compromise the seroprotection rate achieved following primary and booster immunization in individuals receiving either the pentavalent or hexavalent vaccine.