Background: Clinically significant hepatitis B (HB) virus infection has been documented among immunocompromised patients who do not maintain anti-hepatitis surface antigen (anti-HBs) concentrations ≥ 10 IU/L after an adequate response to the vaccine. The aims of the study were to understand the kinetics of anti-HBs titers over time in patients with inflammatory bowel disease (IBD) who initially responded to vaccination and to identify factors predictive of losing protective anti-HBs titers.
Methods: Patients with IBD with a response (anti-HBs > 10 IU/L at 1-3 months) to HB virus vaccination were prospectively included. Anti-HBs titers were measured at 6 and 12 months. Anti-HBs titers were considered negative if they were <10 IU/L at any time during the follow-up. The kinetics of anti-HBs titers in the long term was estimated using Kaplan-Meier curves. Cox regression analysis was performed to identify the factors predictive of losing protective anti-HBs titers.
Results: The sample comprised 100 patients (mean age, 42 years; 68% Crohn's disease; 49% on thiopurines; and 14% on anti-tumor necrosis factors during follow-up). The cumulative incidence of loss of anti-HBs titers was 2% after 6 months and 15% after 12 months. The incidence rate of loss of protective anti-HBs titers was 18% per patient-year. Baseline (after vaccination) anti-HBs titers were lower among patients whose titers became negative during the follow-up than among those who maintained them >10 IU/L (191 versus 515 IU/L; P < 0.001). Treatment with anti-TNFs was the only factor associated with a higher risk of loss of anti-HBs (hazard ratio = 3.1; 95% confidence interval = 1.1-8.8; P = 0.03).
Conclusions: A high proportion of patients with IBD with protective anti-HBs titers after vaccination lose them over time (18% per patient-year of follow-up). The risk of losing protective anti-HBs titers is 3-fold higher among patients on anti- tumor necrosis factors therapy.