How Does Maternal Tdap Vaccination Affect Infants’ Immune Response?

Immunization with the tetanus-diphtheria-acellular pertussis vaccine (Tdap) during pregnancy was associated with increased levels of antibodies in infancy but lower levels following the primary vaccine series, according to the results of a recent study.

While immunization of pregnancy women with Tdap has been shown to provide protection against pertussis in newborns, the effects of this on the infant’s immune response to primary vaccination at 2, 4 and 6 months and booster vaccination at 12 months of age are unknown.

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They conducted a randomized, controlled, observer-blind, multicenter clinical trial involving 273 women receiving either Tdap or tetanus-diphtheria (Td) vaccine in the third trimester. These participants provided information for the safety analysis and, along with 261 infants, provided serum for the immunogenicity analyses.

Overall, infants of mothers who received Tdap 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). They also had significant higher PT antibody levels at birth and 2 months and significantly higher FHA, PRN, and FIM antibody levels 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 those infants whose mothers received Td.

These differences persisted at one month postbooster for PT, FHA, and FIM.

“This study demonstrated that Tdap during pregnancy results in higher levels of antibodies early in infancy but lower levels after the primary vaccine series,” they concluded.

—Michael Potts

Reference:

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 July 13, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy244.