Preliminary data on Response to Tdap immunization in pregnant women with Multiple Sclerosis

Abstract Tetanus-diphtheria-pertussis (Tdap)vaccine is worldwide recommended between 27-36 th week of pregnancy to confer active protective immunity to mothers and passive immunity to neonates. Evidence on response to vaccination in pregnant women with autoimmune diseases as Multiple Sclerosis(MS) is missing. Aim of this study was to evaluate the response to Tdap in MS women untreated or exposed to anti-CD20 therapy before pregnancy. Between 2020 and 2024,37pregnant women(median age 35(31-38))with MS were enrolled at the MS Center,Tor Vergata University(Rome). Serum samples were obtained before vaccination during II trimester of pregnancy(T0), after Tdap within 2weeks(T1) and 3 months(T2) post-partum. Anti-diphteria toxin(DT) and anti-pertussis toxin(PT) IgG titres were measured. Descriptive statistics and non parametric tests were performed. FISM-Fondazione Italiana Sclerosi Multipla-supported the study. 29(78.4%) women(4 treated with anti-CD20) got Tdap vaccine. At T0 only 8(22.2%) women were not protected against dipheria, while 25 had no pertussis protection(71.5%). Seroprotection against diphtheria(>0.1IU/ml) was achieved in 75% of both untreated and treated vaccinated women. Median DT IgG values were higher, but not significantly, for untreated vs treated women(0.256(0.039-0.721) vs0.112(0.018-0.101)at T1 and 0.265(0.117-0.959)vs 0.080(0.017-0.100)at T2). For PT IgG, the seroconversion was reached by 66.6%(16/24) of untreated vaccinated women and by 50%(2/4) of treated women. Our findings suggest that pregnant women with MS, both untreated and anti-CD20 exposed, can mount adequate immune responses to Tdap. Although treated women were protected, the antibody levels were lower and this may correspond to a lower antibody maternal transfer to the newborn. Further data are needed to confirm these findings that might help in tailoring immunization programs and specific public health strategies for frail populations with chronic diseases and exposed to different therapies Key messages • Few data on response to Tdap vaccination in pregnant women with Multiple Sclerosis(MS) are available. • Preliminar data suggest that Tdap vaccination induce a protection also in pregnant women with multiple sclerosis treated and not treated with anti-CD20 therapy.