Rationale: Patients with MS are possibly more vulnerable to infection with SARS-CoV-2. Furthermore the use of immunomodulatory treatment could have an effect on the course of COVID-19 disease. This has resulted in an alteration of current immunomodulatory treatment strategies and delaying the start of certain medications, which could induce MS disease activity. However, certain immunomodulatory treatments are also hypothesized to have a positive effect on COVID-19 disease. Besides lack of information regarding the effects of MS treatments on COVID-19, there is significant uncertainty in how we should advise MS patients in terms of self-isolation, resulting in many patients staying at home reluctant to perform their work or other daily activities. Nationally and locally, we are collecting information regarding COVID-19 in MS patients but numbers are low and only those who are severely affected are tested. Furthermore, there is no information regarding SARS-CoV-2 immunity in MS patients, which could be affected by certain MS treatments. Consequently, there is an urgent need for reliable information about infection rates/immunity and course of COVID-19 in relation to MS characteristics and treatments.

Objectives: The objectives of this study are 1. to study the course of COVID-19 in MS patients in relation to immunomodulatory treatment and other patient and MS characteristics and 2. to study the proportion of MS patients with SARS-CoV-2 antibodies and 3. to establish the antibody profile in positive tested patients and 4. to study the longitudinal course of these antibody profiles in positive tested patients.

Study design: This is a mono-center cohort study in patients of the MS Center Amsterdam.

Study population: All patients with a diagnosis of MS currently under follow-up in the Amsterdam MS Center.

Intervention (if applicable): Single venous puncture for drawing blood and questionnaire. For a minority of patients (max 25%) who test positive for antibodies we will draw blood a again with questionnaires after six and twelve months.

Main study parameters/endpoints: Course of COVID-19 in MS patients in relation to MS immunomodulatory treatment.

Inclusion Criteria:

• a current diagnosis of multiple sclerosis and age ≥18 years.

Exclusion Criteria:

• lack of informed consent.

All patients with a diagnosis of MS currently under follow-up in the MS Center Amsterdam.