Study to Investigate the Immune Response to Influenza Vaccine in Patients With Multiple Sclerosis on Teriflunomide Treatment and Using a Population of Patients With Multiple Sclerosis as a Reference

Primary Objective:Assess the antibody response to influenza vaccine in patients with relapsing form of multiple sclerosis (RMS) treated with teriflunomide compared to a reference population.Secondary Objectives:* Assess the effect of teriflunomide on immunoglobulin levels;* Assess the safety of influenza vaccination in patients with RMS treated with teriflunomide.The reference population was defined as multiple sclerosis (MS) patients with a stable treatment with interferon-β-1. Antibody response was measured using hemagglutination inhibition assay (HIA) and the hemagglutinin antigens representing the stains of H3N2, H1N1, and B as present in the influenza vaccine used.