Immune Response to Seasonal Influenza Vaccine in Patients with Relapsing-Remitting Multiple Sclerosis Receiving Long-term Daclizumab Beta: A Prospective, Open-Label, Single-Arm Study.

BACKGROUND:For patients with relapsing-remitting multiple sclerosis (RRMS) undergoing continuous immunomodulatory therapy, understanding whether vaccinations can be performed safely and effectively is important. We tested the immune response to inactivated seasonal influenza vaccine during long-term daclizumab beta treatment.METHODS:In this prospective, open-label, single-arm extension SELECTED study, an optional vaccine substudy was performed on patients with RRMS who had already received daclizumab beta for 1 to 2 years in previous studies. Patients were administered the seasonal vaccine as a single intramuscular dose containing three inactivated influenza virus strains: A/California/7/2009 (A/H1N1), A/Texas/50/2012 (A/H3N2), and B/Massachusetts/2/2012 (B). Endpoints included proportion of patients achieving seroprotection, proportion of patients who seroconverted, geometric mean titer ratio before and after vaccination, and adverse events reported during 28-day follow-up.RESULTS:Ninety patients received the influenza vaccine (mean previous daclizumab beta exposure, 49.6 doses). Seroprotection (anti-hemagglutination immunoglobulin G titer ≥40) was detected in 92% (95% confidence interval [CI], 85%-97%) of patients for A/H1N1, 91% (83%-96%) for A/H3N2, and 67% (56%-76%) for B. The proportion of patients who seroconverted was 69% (95% CI, 58%-78%) for A/H1N1, 69% (58%-78%) for A/H3N2, and 44% (34%-55%) for B. The anti-hemagglutination immunoglobulin geometric mean titer ratio was 7.7 for A/H1N1, 9.0 for A/H3N2, and 4.3 for B. There were no significant adverse events considered related to vaccination during 28-day follow-up.CONCLUSIONS:Patients with RRMS receiving long-term daclizumab beta treatment mounted an immune response to the seasonal influenza vaccine at levels considered to confer protection. No major or new safety issues were identified.