The purpose of this study is to evaluate the safety and reactogenicity of mRNA-1195 in healthy participants.

There will be 2 sequential parts to the study:

• Participants 18 through 55 years of age will be enrolled in Part A of the study first, which will only enroll those participants who are EBV-seropositive at Screening.
• Part B will enroll participants 18 through 30 years of age who are either EBV-seronegative or EBV-seropositive at Screening.

Key Inclusion Criteria:

• For Part A: Positive EBV serostatus at Screening. For Part B: Negative EBV serostatus or Positive EBV serostatus at Screening.
• According to the assessment of the Investigator, is in good general health and can comply with study procedures.
• For 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, agreement to continue adequate contraception through 3 months following last study injection and is not currently breast/chest feeding.

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 or authorized vaccine, to include COVID-19 vaccines, ≤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 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.