Reduced antibody formation after influenza vaccination in patients with neuromyelitis optica spectrum disorder treated with rituximab

Background and purpose: Vaccination against infection becomes important in patients with neuromyelitis optica spectrum disorder (NMOSD) because they are at an increased risk of infection due to long-term immunosuppressive therapy. However, it is unclear whether NMOSD patients under immunosuppression therapy show proper antibody formation after vaccination. Thus the antibody formation after influenza A (H1N1) vaccination in patients with NMOSD receiving rituximab was evaluated. Methods: The study enrolled 26 patients with NMOSD, nine with multiple sclerosis and eight healthy controls. The enrolled patients had been treated with rituximab (n = 16), mycophenolate mofetil (n = 5), azathioprine (n = 6) and interferon-β (IFN-β) (n = 8). Antibodies against the H1N1 influenza virus were measured in the serum drawn just before (T0) and between 3 and 5 weeks after (T1) vaccination. The immunization states for hepatitis B virus surface antigen, measles and tetanus during the treatment period were also tested. Results: The rituximab group showed significantly lower geometric mean titer, seroprotection rate and mean fold increase than the azathioprine group, IFN-β group and healthy controls, and a lower seroconversion rate than the IFN-β group. This decrease in vaccination efficacy was also shown in patients receiving mycophenolate mofetil. The immunization state for hepatitis B virus surface antigen, measles and tetanus remained the same during the treatment period with each drug, suggesting that these treatments do not affect previously formed immunity. Conclusion: This study shows a severely hampered humoral immune response to H1N1 influenza vaccine in patients with NMOSD treated with rituximab, although the vaccination itself is safe in these patients.