Inclusion criteria  The participant must have a previous diagnosis of RMS in accordance with the 2017 revised McDonald criteria The participant must have been newly prescribed to OCR treatment according to clinical practice Absence of high dose of steroid treatment for at least 4 weeks The participant must be capable of giving signed informed consent.  Exclusion criteria  Clinical MS relapse within four-week period prior to inclusion Pregnant or nursing (lactating) women. Chronic disease of the immune system, other than MS Active systemic bacterial, viral or fungal infections Allergy to OCR Already included in other interventional trials