(Part A and B): ● Patient is outside of infectious period of COVID-19 defined as follows: - Patient with mild to moderate illness who are not severely immunocompromised: - At least 10 days have passed since symptoms first appeared and - At least 24 hours have passed since last fever without the use of fever-reducing medications and - Symptoms (e.g. cough, shortness of breath) have improved - Patient with severe to critical illness or who are severely immunocompromised: - At least 10 days and up to 20 days have passed since symptoms first appeared - At least 24 hours have passed since last fever without the use of fever-reducing medications and - Symptoms (e.g. cough, shortness of breath) have improved - Clinician-diagnosed MS treated or untreated with an approved DMT, - Ages 18 to 60, - EDSS 0 - 7, - Able to give informed consent, - Able to complete, or have someone help complete the patient questionnaire, - No high dose steroids, or IVIG, or PLEX use within 3 months of blood sample, - No convalescent plasma and/or polyclonal antibody treatments for COVID-19 within 3 months of blood sample collection. Inclusion Criteria (Part B only) - COVID-19 positive patients, who received OCR within 6 months of COVID 19 infection, - EDSS 0 - 6. Inclusion Critera (Redraws Only) - Completed standard of care COVID-19 vaccination series - On Ocrevus, glatiramer, interferon b, or not on any treatment disease-modifying treatment at the time of vaccination.

(Part A and B): - Concurrent immunosuppressive therapy, active systemic cancer, primary or acquired immunodeficiency (i.e., CVID, HIV infection), - Active drug or alcohol abuse, - Other anti-CD20 therapy apart from OCR, - Uncontrolled diabetes mellitus, - End-organ failure (cardiac, pulmonary, renal, hepatic), - Systemic lupus erythematosus (SLE). Exclusion Criteria (Part B only): - EDSS >6, - Active infection (e.g., hepatitis). Exclusion Criteria (Healthy Controls Sample) - Concurrent immunosuppressive therapy, active systemic cancer, primary or acquired immunodeficiency (e.g. CVID, HIV infection), - Active ongoing drug or alcohol abuse, - Age >60 or <18, - Uncontrolled diabetes mellitus, - End-organ failure (cardiac, pulmonary, renal, hepatic), - SLE - No high dose steroids, or intravenous immunoglobulin (IVIG) or plasma exchange (PLEX) use within 3 months of blood sample collection, - No convalescent plasma and/or polyclonal antibody treatments for COVID-19 within 3 months of blood sample collection.