Association Between Third-Trimester Tdap Immunization and Neonatal Pertussis Antibody Concentration

Area of Science:

• Immunology
• Maternal-Fetal Medicine
• Vaccinology

Background:

• Infant pertussis poses a life-threatening risk, necessitating maternal immunization with the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine during pregnancy (weeks 27-36).
• The optimal timing for Tdap vaccination during pregnancy to maximize neonatal antibody levels remains undetermined.

Purpose of the Study:

• To compare pertussis toxin antibody concentrations in neonates born to mothers who received Tdap vaccine during pregnancy versus those who did not.
• To identify the optimal gestational age for maternal Tdap immunization to achieve peak neonatal antibody levels.

Main Methods:

• A prospective, observational cohort study was conducted with term neonates in Houston, Texas.
• Cord blood samples were analyzed for pertussis toxin antibody concentrations in neonates from Tdap-immunized and unimmunized mothers.
• Gestational age at the time of maternal Tdap vaccination was recorded and analyzed.

Main Results:

• Maternal Tdap immunization was associated with significantly higher geometric mean concentrations (GMCs) of neonatal pertussis toxin antibodies (47.3 IU/mL vs. 12.9 IU/mL).
• A greater proportion of neonates born to Tdap-vaccinated mothers had antibody concentrations of 15 IU/mL or higher (86% vs. 37%), 30 IU/mL or higher (72% vs. 17%), and 40 IU/mL or higher (59% vs. 12%).
• The highest GMCs of neonatal antibodies were observed when maternal Tdap vaccination occurred between 27 and 30 weeks of gestation, peaking at 30 weeks.

Conclusions:

• Third-trimester maternal Tdap vaccination significantly increases neonatal pertussis toxin antibody concentrations.
• Administering the Tdap vaccine earlier in the third trimester (weeks 27-30) is associated with the highest antibody levels in newborns, potentially offering enhanced protection.