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Immunogenicity of Tdap During Pregnancy
Clin Infect Dis; ePub 2018 Jul 13; Halperin, et al
Administration of tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy results in higher levels of antibodies early in infancy but lower levels after the primary vaccine series, a recent study found. In a randomized, controlled clinical trial, researchers 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. They found:
- 273 women received either Tdap or tetanus-diphtheria (Td) vaccine in the third trimester and provided information for the safely analysis and samples for the immunogenicity analysis; 261 infants provided serum for the immunogenicity analyses.
- 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 ad FHA antibody levels at 6 and 7 months and significantly lower PRN and FIM antibody levels as 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.
Halperin Sa, Langley JM, Ye L, et al. A randomized controlled trial of the safety and immunogenicity of tetanus, diphtheria, and acellular pertussis vaccine immunization during pregnancy and subsequent infant immune response. [Published online ahead of print July 13, 2018]. Clin Infect Dis. doi:10.1093/cid/ciy244.
This was an interesting study. Overall it showed that the infants of women who received the Tdap vaccine during the third trimester produced higher serologic immunity against pertussis in the first few months after birth. These same infants had a more blunted response to the pertussis containing vaccine that they received in the first 6 months of life. The study did not continue long enough to show if this blunted effect persisted. Since most pertussis fatalities occur in the first 3 months of age, it would make sense to continue to vaccinate pregnant women with the Tdap vaccine. It will also be interesting to see if this decreased response continues through the rest of childhood, so we can be better informed in making decisions about schedules and recommendations for the DTaP vaccine. —John Russell, MD