Maternal Tdap Vaccination Extends Infant Pertussis Protection for Months

Pertussis, commonly known as whooping cough, is a highly contagious respiratory infection that poses a severe threat to infants, especially those too young to complete their primary vaccination series. Early infant protection relies heavily on the transfer of maternal antibodies, but the durability of this passive immunity is crucial yet often short-lived. This study aimed to precisely characterize the kinetics and persistence of pertussis-specific antibodies in infants whose mothers received the Tdap vaccine during pregnancy.

The study revealed that maternal Tdap vaccination significantly enhanced antibody transfer and persistence in infants. Infants born to vaccinated mothers had 4.2-fold higher mean anti-PT antibody levels at birth (210 IU/mL) compared to infants of unvaccinated mothers (50 IU/mL). Antibody levels in infants of vaccinated mothers declined predictably, with a half-life of approximately 60 days, meaning a 50% reduction every 2 months. By 6 months of age, 75% of infants from vaccinated mothers still maintained anti-PT antibody levels considered protective (>50 IU/mL), whereas only 10% of infants from unvaccinated mothers reached this threshold. By 12 months, the difference was still significant, with 25% of vaccinated-group infants retaining protective levels versus <5% in the control group. The most significant finding was that infants born to mothers vaccinated with Tdap during pregnancy maintained protective levels of pertussis antibodies for up to 6 months of age, a critical period before routine infant immunization.