An observational, cohort, multi-centre, open label phase IV extension study comparing IPV immune responses to preschool dTaP-IPV booster vaccines in children whose mothers received or did not receive an IPV-containing pertussis vaccine during pregnancy in England.

A diphtheria-tetanus-acellular pertussis-inactivated polio combination vaccine (dTaP-IPV) was offered as part of the UK antenatal vaccination programme from 2012 to July 2024. Prior research established that infants of mothers who received a dTaP-IPV vaccine in pregnancy have significantly reduced poliovirus-specific neutralising antibodies after their primary immunisation series compared with infants of non-dTaP-IPV vaccinated mothers. We investigated whether sufficient poliovirus-specific neutralising antibody titres are achieved in these children following the pre-school dTaP-IPV booster vaccine. Poliovirus-specific neutralising antibody titres were measured, via a microneutralisation assay, prior to and following receipt of the pre-school booster vaccine in blood samples taken during an observational, cohort, multi-centre, open label phase IV extension study. Prior to the pre-school boost, children of mothers who received dTaP-IPV vaccines in pregnancy had lower geometric mean titres (GMT) of antibodies than children of unvaccinated mothers (4.3 vs 54.7, p = 0.0001). However, following administration of the pre-school booster all children, regardless of maternal vaccination status achieved protective antibody titres (≥ 8), although children of vaccinated mothers still had lower GMTs (988 vs 2964, p = 0.009). Administration of the preschool booster overcomes the polio virus immunity gap that develops following the primary vaccination series in children whose mothers received an antenatal dTaP-IPV vaccine versus unvaccinated mothers. Residual differences in post-booster titres warrant continued surveillance to assess their clinical relevance. Clinical trials registry:NCT03578120.