A Multicenter Study to Assess Response to Influenza Vaccine in Multiple Sclerosis Participants Treated With Ofatumumab

Vaccinations against influenza are an important part of effective management of multiple sclerosis (MS). Ofatumumab is a human anti-CD20 monoclonal antibody (mAb) which depletes B-cells, a component of the immune system. This study investigates if ofatumumab treated patients can have an immune response that may be protective after receiving the influenza vaccine. There were 3 study periods: * Screening Period of up to 1 week to assess eligibility requirements. * Investigational Period of 4 weeks All participants received an inactivated influenza vaccine within 9 calendar days after the Screening Visit, before the Week 0 Visit occurred. Participants in Cohort 1 received loading doses of 20 mg ofatumumab administered subcutaneously (s.c.) at Weeks 2, 3, and 4. Participants in Cohort 2 continued taking their prescribed ofatumumab as per their dosing schedule throughout the Investigational Period. Participants in Cohort 3 continued administration of their prescribed injectable disease modifying therapy (iDMT) as per their dosing schedule in the Investigational Period. • Optional, 6-month open-label Extension Period Participants in Cohort 1 were administered their first dose of ofatumumab at Week 6; thereinafter, they continued monthly dosing until the final dose at Week 26. Participants in Cohort 2 continued to receive ofatumumab monthly until the final dose at Week 28. Participants in Cohort 3 did not enter the open-label Extension Period.