P318. Kinetics of the anti-HBs titers after vaccination against hepatitis B virus (HBV) in patients with inflammatory bowel disease (IBD)
J.P. Gisbert1, J.R. Villagrasa2, A. Rodríguez-Nogueiras2, M. Chaparro1
1Hospital Universitario de La Princesa, IP, Gastroenterology and CIBEREHD, Spain; 2Hospital De La Princesa, Madrid, Spain
Background: Among immunocompromised patients who respond to the vaccine, clinically significant HBV infection has been documented in those who do not maintain anti-HBs concentrations = 10 IU/l.
Objectives: (i) To understand the kinetics of the anti-HBs titers over time in IBD patients who have responded initially to the vaccination. (ii) To identify predictive factors of negativization of anti-HBs titers.
Methods: Patients from our IBD Unit with anti-HBs >10 IU/l after HBV vaccination were prospectively included. Vaccination protocol consisted on a double dose of Engerix B® at 0, 1 and 2 months. Anti-HBs titers were measured 1–3 months after the last vaccine dose. Patients with anti-HBs <100 IU/l after the 1st attempt were considered failures and were vaccinated again with the same protocol. Patients with anti-HBs >10 UI/l after the 1st or 2nd vaccination were followed-up. Anti-HBs titers were measured at 6 and 12 months. When anti-HBs titers were lower than 10 UI/l during the follow-up, they were considered negatives. Long-term maintenance of positive anti-HBs titers was estimated using Kaplan–Meier curves. Cox-regression analysis was performed to identify potential predictive factors for losing anti-HBs protective titers.
Results: 100 patients were included (mean age 42 years, 53% females, and 68% Crohn's disease). 49% were on thiopurines, and 14% on anti‑TNF drugs. 33 patients (33%) had received two vaccination attempts. Basal anti-HBs titers were >100 UI/l in 88% of patients. The cumulative incidence of negativization of the anti-HBs titers was 2% after 6 months and 15% after 12 months from the basal determination. The incidence rate of negativization of the anti-HBs titers was 18% per patient-years. Anti-HBs basal titers were statistically significant lower among patients who had negative values thereafter during the follow-up, compared with those who maintained them over 10 IU/l (191 IU/l vs. 515 IU/l, p < 0.001). In the multivariate analysis, neither the patient's age, gender, type of IBD or the treatment with thiopurines were associated with a higher probability of negativization of anti-HBs titers. The treatment with anti‑TNF drugs was the only factor associated with a higher risk of negativization of anti-HBs titers (HR=3.1, 95%CI=1.1–8.8, p = 0.03).
Conclusions: A high proportion of IBD patients with protective anti-HBs titers after vaccination lose them over time (18% of patients per year of follow-up). The risk of losing protective anti-HBs titers is 3‑fold higher among IBD patients on anti‑TNF therapy.