Risk of hepatitis B virus reactivation in people with multiple sclerosis treated with ocrelizumab: an observational study from Turkey

Background The risk of hepatitis B virus (HBV) reactivation remains unclear in people with multiple sclerosis (MS) receiving ocrelizumab. We aimed to assess HBV seroprevalence and reactivation risk in MS patients on ocrelizumab and to evaluate the effectiveness of antiviral prophylaxis against HBV reactivation. Methods In this single-center, cross-sectional study, 400 people with MS receiving ocrelizumab were screened for HBV at baseline and antiviral prophylaxis was implemented based on serological results. Patients were monitored for HBV reactivation, and outcomes were analyzed. Results Among 56 (14%) patients who had serology compatible with occult or resolved HBV infection, 49 (85.7%) received antiviral prophylaxis regularly and had no HBV reactivation during the follow-up. Reactivation of HBV occurred in 2 out of 7 (28.6%) patients who did not receive antiviral prophylaxis and in one patient who did not adhere to the prophylaxis regimen. All patients with reactivation had anti-HBs levels below 100 mIU/mL and the median titer was significantly lower than the patients with no HBV reactivation ( p = 0.034). Conclusion This study highlights a 14% anti-HBc positivity, indicating a potential risk for HBV reactivation in people with MS receiving ocrelizumab. This suggests the importance of vigilant monitoring and the implementation of prophylactic measures. Our recommendation emphasizes antiviral prophylaxis, particularly for patients with low anti-HBs, and a pre-emptive strategy for others.