A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose-Ranging Study of mRNA-1195 Intramuscular Injection in Participants 18 to ≤55 Years of Age With Multiple Sclerosis

Inclusion Criteria: * Medically stable as determined by Investigator's medical evaluation, which will include assessment of medical history, physical examination, laboratory testing, and review of any previously conducted cardiac monitoring. * Participants who are Epstein-Barr virus (EBV)-seropositive at screening. * Participants diagnosed with relapsing multiple sclerosis, including those with a single clinical attack (that is, clinically isolated syndrome \[CIS\]), as well as participants diagnosed with radiologically isolated syndrome, within 24 months of Screening Visit (that is, early in…