A Study of an Epstein-Barr Virus (EBV) Candidate Vaccine, mRNA-1195, in 18- to 55-Year-Old Healthy Adults

Key Inclusion Criteria: For Part A: Positive EBV serostatus at Screening. For Part B: Negative EBV serostatus at Screening. According to the assessment of the Investigator, is in good general health and can comply with study procedures. For female participants of childbearing potential: negative pregnancy test, adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to Day 1, and agreement to continue adequate contraception through 3 months following vaccine administration. Key Exclusion Criteria: Participant is acutely ill or febrile (temperature ≥38.0 degrees Celsius [°C]/100.4 degrees Fahrenheit [°F]) 72 hours prior to or at the Screening Visit or Day 1. Symptomatic acute or chronic illness requiring ongoing medical or surgical care, to include changes in medication in the past 2 months indicating that chronic illness/disease is not stable (at the discretion of the Investigator). Any medical, psychiatric, or occupational condition, including reported history of drug or alcohol abuse, that, in the opinion of the Investigator, might pose additional risk due to participation in the study or could interfere with the interpretation of study results. History of myocarditis, pericarditis, or myopericarditis. Participant has received systemic immunosuppressants or immune-modifying drugs for >14 days in total within 6 months prior to Screening Visit (for corticosteroids ≥10 milligrams [mg]/day of prednisone or equivalent) or is anticipating the need for immunosuppressive treatment at any time during participation in the study. Topical corticosteroids and tacrolimus are allowed. Participant has received or plans to receive any licensed vaccine ≤28 days prior to the first injection (Day 1) or plans to receive a licensed vaccine within 28 days before or after any study injection, with the exception of licensed/authorized influenza or SARS-CoV-2 vaccines, which may be received more than 14 days before or after any study injection. Participant has donated ≥450 milliliters (mL) of blood products within 28 days prior to the Screening Visit or plans to donate blood products during the study. Note: Other inclusion and exclusion criteria may apply.