The Effect of Pertussis Vaccination During Pregnancy on Pertussis and Diphtheria Immunity in Children at 3 and 4 Years of Age.

Pertussis vaccination during pregnancy protects young infants but blunts their antibody responses to primary immunization; the duration of this effect beyond infancy is unknown. In a clinical trial, we followed children born to tetanus-diphtheria-acellular pertussis-vaccinated (n=47) and unvaccinated (n=22) mothers to 4 years of age. At both 3 and 4 years, children born to Tdap-vaccinated mothers had lower anti-pertussis toxin and anti-diphtheria toxin IgG concentrations than control children, and pertussis toxin seropositivity and diphtheria seroprotection rates were low in both groups. After a preschool acellular pertussis booster at 4 years, antibody concentrations increased to comparable levels in both groups.