An observational, cohort, multi-centre, open label phase IV extension study comparing preschool DTAP-IPV booster vaccine responses in children whose mothers were randomised to one of two pertussis-containing vaccines or received no pertussis-containing vaccine in pregnancy in England

• Evaluated children's antibody responses prior to and following the receipt of the dTaP5-IPV preschool booster, to all of the antigenic component of the vaccine (pertussis toxin, filamentous haemagglutinin, fimbriae 2 & 3, pertactin, diphtheria toxoid and tetanus toxoid). • Evaluated and compared the impact of two antenatal pertussis-containing vaccines, dTaP3-IPV and dTaP5-IPV, on children's own vaccine responses to the receipt of the dTaP5-IPV preschool booster. • Evaluated the blunting effect of antenatal pertussis vaccination on children's own vaccine responses persisting up to around the age of 3 and a half years old. • The first study to evaluate on the impact of antenatal pertussis vaccination on children's own vaccine responses beyond the age of 2 years old. An antenatal pertussis vaccination programme was introduced in 2012 in the UK in the context of a national outbreak of pertussis. It has been shown that a lower antibody response to primary immunisation can be seen for certain pertussis antigens in infants born to women who received pertussis-containing antenatal vaccines, a phenomenon known as blunting. The longer-term impact of this has not been documented previously, and accordingly was evaluated in this study. Children were predominantly recruited from a previous study in which their mothers had received acellular pertussis-containing antenatal vaccines (dTaP 3 -IPV [diphtheria toxoid, tetanus toxoid, three antigen acellular pertussis and inactivated polio] or dTaP 5 -IPV [diphtheria toxoid, tetanus toxoid, five antigen acellular pertussis and inactivated polio]), or no pertussis-containing vaccine. Blood samples were obtained prior to and one month after the acellular pertussis-containing preschool booster (dTaP 5 -IPV) was given at around age 3 years 4 months. Pre- and post-booster immunoglobulin G (IgG) geometric mean concentrations (GMCs) against pertussis toxin, filamentous haemagglutinin, fimbriae 2 & 3, and pertactin, were compared. Prior to the receipt of the preschool booster, there was no difference in the IgG GMCs against pertussis-specific antigens between children born to women vaccinated with dTaP 3 -IPV and dTaP 5 -IPV; however, IgG GMCs against pertussis toxin were significantly lower in children born to women vaccinated with dTaP 3 -IPV compared with children born to unvaccinated women (geometric mean ratio 0.42 [95 % CI 0.22–0.78], p = 0.03). One month after the receipt of the preschool booster there was no differences between the groups. The blunting effect of antenatal pertussis vaccine on pertussis responses in children can persist until preschool age, although it is overcome by the administration of a booster dose. ClinicalTrials.gov registration number: NCT03578120 [ABSTRACT FROM AUTHOR]