Durability of the anti-hbs titers after vaccination against Hepatitis B virus (HBV) in patients with inflammatory bowel disease (IBD) M. Chaparro 1, J. Gordillo 2, E Domènech 3, M Esteve 4, M. Barreiro de-Acosta 5, A. Villoria 6, E. Iglesias-Flores 7, M. Blasi 2, J.E. Naves 3, O. Benítez 4, L. Nieto 5, X. Calvet 6, V. García-Sánchez 7, J.R. Villagrasa 8, A.C. Marín 1, M. Ramas 1, I. Moreno 9, J.P. Gisbert 1. 1 Gastroenterology Unit. Hospital Universitario de La Princesa, IIS-IP and CIBERehd. Madrid. 2 Gastroenterology Unit. Hospital Santa Creu i Sant Pau. Barcelona. 3 Gastroenterology Unit. Hospital Universitario Germans Trias i Pujol and CIBERehd. Badalona. 4 Gastroenterology Unit. Hospital Universitario Mutua de Terrassa and CIBERehd. Terrassa. 5 Gastroenterology Unit. Complejo Hospitalario Universitario de Santiago. Santiago de Compostela. 6 Gastroenterology Unit. Hospital de Sabadell. and CIBERehd. Sabadell. 7 Gastroenterology Unit. Hospital Universitario Reina Sofía. Córdoba. 8 Preventive Medicine Unit. Hospital Universitario de La Princesa and IIS-IP. Madrid. 9 Foundation for Biomedical Research. Hospital Universitario de La Princesa and IIS-IP. Madrid. Spain Among immunocompromised patients who respond to the HBV vaccine, clinically significant HBV infection has been documented in those who do not maintain anti-HBs concentrations > 10 IU/l. 1)To understand the kinetics of the anti-HBs titers over time in IBD patients who have initially responded to the vaccination. 2)To identify predictive factors of negativization of anti-HBs titers over time. 1)To understand the kinetics of the anti-HBs titers over time in IBD patients who have initially responded to the vaccination. 2)To identify predictive factors of negativization of anti-HBs titers over time. 132 patients were included (median age 48 years, 55% males, 49% Crohn’s disease and 51% ulcerative colitis). Thirty-one percent of patients were on immunomodulators, and 32% on anti-TNF drugs. Fifty percent of patients received each of the vaccines (Engerix  or Fendrix  ). The cumulative incidence of negativization of the anti-HBs titers was 15% after 6 months and 21% after 12 months of follow-up. The incidence rate of negativization of the anti-HBs titers was 23% per patient-years of follow-up. The type of vaccine administered was not associated with a different risk of negativization of anti-HBs titers. 132 patients were included (median age 48 years, 55% males, 49% Crohn’s disease and 51% ulcerative colitis). Thirty-one percent of patients were on immunomodulators, and 32% on anti-TNF drugs. Fifty percent of patients received each of the vaccines (Engerix  or Fendrix  ). The cumulative incidence of negativization of the anti-HBs titers was 15% after 6 months and 21% after 12 months of follow-up. The incidence rate of negativization of the anti-HBs titers was 23% per patient-years of follow-up. The type of vaccine administered was not associated with a different risk of negativization of anti-HBs titers. This multicenter study included IBD patients vaccinated in the COMVI-B trial (EUDRA CT number: ), where patients with negative HBV serology and without previous vaccination against HBV were randomized 1:1 to receive Fendrix  or double doses of Engerix  at months 0, 1, 2 and 6. Patients with anti-HBs > 10 IU/l 2 months after the 4 th dose were followed-up. Anti-HBs titers were then measured at 6 and 12 months. When anti-HBs titers were < 10 IU/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 during follow-up. This multicenter study included IBD patients vaccinated in the COMVI-B trial (EUDRA CT number: ), where patients with negative HBV serology and without previous vaccination against HBV were randomized 1:1 to receive Fendrix  or double doses of Engerix  at months 0, 1, 2 and 6. Patients with anti-HBs > 10 IU/l 2 months after the 4 th dose were followed-up. Anti-HBs titers were then measured at 6 and 12 months. When anti-HBs titers were < 10 IU/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 during follow-up. 1. Background 2. Aims 3. Methods 4. Results A high proportion of IBD patients with protective anti-HBs titers after vaccination lose them over time (approximately, 25% of patients per year of follow-up). The risk of losing protective anti-HBs titers is dramatically increased in patients achieving anti-HBs below 100 IU/l after the vaccination. Thus, anti-HBs > 100 IU/l should be the threshold to consider HBV vaccination success in IBD patients. A high proportion of IBD patients with protective anti-HBs titers after vaccination lose them over time (approximately, 25% of patients per year of follow-up). The risk of losing protective anti-HBs titers is dramatically increased in patients achieving anti-HBs below 100 IU/l after the vaccination. Thus, anti-HBs > 100 IU/l should be the threshold to consider HBV vaccination success in IBD patients. 5. Conclusions Patients maintaining anti-HBs >10 IU/l 85% 79% Follow-up (months) % 75 % 50% 25% 0% Table 1. Multivariate analysis of factors association with the negativization of anti-HBs. Cumulative incidence of negativization of anti-HBs.