Inclusion Criteria:  Diagnosis of clinically definite multiple sclerosis (CDMS) by the 2017 McDonald Criteria 38; Age greater than or equal to 18 years; Ability to travel to Griffin Hospital for phlebotomyand booster vaccination; Completion of a COVID-19 vaccine series at least 4 weeks prior to booster randomization; Willing to undergo a booster vaccination with either BNT162b2, mRNA-1273 or Ad26.COV2.S.  Exclusion Criteria:  Inability to give consent; Non-fluency in English; Inability to adhere to the protocol; Anticipated life expectancy of less than six months; Lack of a primary care physician or treating neurologist; Taking an immunosuppressive medication or chemotherapy for any other conditions aside fromMS; Presence of another autoimmune condition requiring treatment; Active treatment for cancer;  History of heavy alcohol use within the past year, as defined by the following criteria:  Men: 5 or more alcoholic beverages per session or per day, or 15 or more per week; Women: 4 or more alcoholic beverages per session or per day, or 8 or more per week; History of illicit drug abuse, e.g., cocaine, heroin, PCP, and/or narcotics within the past year; Any condition that would jeopardize the safety or rights of the subject, make it unlikely for the subject to complete the study, or confound the study results.Anaphylactic or other severe reaction to a previously administered COVID-19 vaccine; Positive urine pregnancy test at screening. Test is waived in women who are post-menopausal or incapable of conception.