Impact of immunomodulating medication on maternal Tdap vaccination-induced antibodies in infants

Current international guidelines on inflammatory bowel disease (IBD) advise to continue immunomodulating medication during pregnancy. Data on the effect of this medication on maternal Tdap (Tetanus-Diphtheria-acellular pertussis) vaccination and transfer of antibodies to the infant are scarce.

Pregnant women with IBD receiving various immunomodulating medications and their infants were prospectively recruited in the Pregnancy Exposure to TNF alpha inhibitors and Immunological effect (PETIT) study cohort from 16 hospitals in the Netherlands between December 2018 and March 2023. All women were offered maternal Tdap vaccination according to the Dutch National Immunization Program. IgG concentrations against all Tdap components were measured at birth (maternal and cord blood) and at 2 months of age in the infant, preceding active immunization. We compared geometrical mean concentrations (GMCs) in IBD mother-infant pairs with healthy control mother-infant pairs.

Geometrical mean concentrations of antibodies against all Tdap components were significantly higher in 135 maternally vaccinated mothers and their infants compared with 25 unvaccinated IBD women-infant pairs treated with immunomodulating medication during pregnancy, at all timepoints. However, GMC against pertactin (PRN) was significantly lower in vaccinated IBD mother-infant pairs compared to healthy vaccinated control mother-infant pairs, particularly in mothers treated with anti-tumor necrosis factor alpha and their infants.

Maternal Tdap vaccination in women with IBD receiving immunomodulating medication during pregnancy results in significantly higher Tdap-antibody concentrations in their infants compared to infants of unvaccinated IBD mothers, although GMC was lower for PRN compared to healthy controls. These results support current recommendations to advise maternal Tdap vaccination in pregnant women receiving immunomodulating medication.