A phase IV, multi-centre, randomized clinical trial comparing two pertussis-containing vaccines in pregnant women in England and vaccine responses in their infants

Background: Pertussis vaccines containing three or five pertussis antigens are recommended in pregnancy in many countries, but no studies have compared the effect on infants' antigen-specific immunoglobulin G (IgG) concentrations. The aim of this study was to compare anti-pertussis IgG responses following primary immunization in infants of mothers vaccinated with TdaP(5)-IPV (low dose diphtheria toxoid, tetanus toxoid, acellular pertussis [five antigens] and inactivated polio) or TdaP(3)-IPV in pregnancy (three pertussis antigens). Methods: This multi-centre phase IV randomized clinical trial was conducted in a tertiary referral centre and primary care sites in England. Women were randomized to receive TdaP(5)-IPV (n = 77) or TdaP(3)-IPV (n = 77) at 28-32 gestational weeks. A non-randomized control group of 44 women who had not received a pertussis-containing vaccine in pregnancy and their 47 infants were enrolled post-partum. Results: Following infant primary immunization, there was no difference in the geometric mean concentrations (GMCs) of anti-pertussis toxin, filamentous haemagglutinin or pertactin IgG between infants born to women vaccinated with TdaP(5)-IPV (n = 67) or TdaP(3)-IPV (n = 63). However, the GMC of anti-pertussis toxin IgG was lower in infants born to TdaP(5)-IPV- and TdaP(3)-IPV-vaccinated mothers compared to infants born to unvaccinated mothers (n = 45) (geometric mean ratio 0.71 [0.56-0.90] and 0.78 [0.61-0.98], respectively); by 13 months of age, this difference was no longer observed. Conclusion: Blunting of anti-pertussis toxin IgG response following primary immunization occurs in infants born to women vaccinated with TdaP(5)-IPV and TdaP(3)-IPV, with no difference between maternal vaccines. The blunting effect had resolved by 13 months of age. These results may be helpful for countries considering which pertussis-containing vaccine to recommend for use in pregnancy.

Automated summary

The study found no significant difference in anti-pertussis IgG concentrations in infants born to mothers vaccinated with TdaP(5)-IPV or TdaP(3)-IPV. However, infants born to unvaccinated mothers had lower anti-pertussis toxin IgG concentrations, which normalized by 13 months of age.