A Randomized Controlled Trial of the Safety and Immunogenicity of Tetanus, Diphtheria, and Acellular Pertussis Vaccine Immunization During Pregnancy and Subsequent Infant Immune Response

Background. Immunization of pregnant women with tetanus-diphtheria-acellular pertussis vaccine (Tdap) provides protection against pertussis to the newborn infant. Methods. In a randomized, controlled, observer-blind, multicenter clinical trial, we measured the safety and immunogenicity of Tdap during pregnancy and the effect on the infant's immune response to primary vaccination at 2,4, and 6 months and booster vaccination at 12 months of age. A total of 273 women received either Tdap or tetanus-diphtheria (Td) vaccine in the third trimester and provided information for the safety analysis and samples for the immunogenicity analyses; 261 infants provided serum for the immunogenicity analyses. Results. Rates of adverse events were similar in both groups. Infants of Tdap recipients had cord blood levels that were 21% higher than maternal levels for pertussis toxoid (PT), 13% higher for filamentous hemagglutinin (FHA), 4% higher for pertactin (PRN), and 7% higher for fimbriae (FIM). These infants had significantly higher PT antibody levels at birth and at 2 months and significantly higher FHA, PRN, and FIM antibodies at birth and 2 and 4 months, but significantly lower PT and FHA antibody levels at 6 and 7 months and significantly lower PRN and FIM antibody levels at 7 months than infants whose mothers received Td. Differences persisted prebooster at 12 months for all antigens and postbooster 1 month later for PT, FHA, and FIM. Conclusions. This study demonstrated that Tdap during pregnancy results in higher levels of antibodies early in infancy but lower levels after the primary vaccine series.