The main objective of Part A of this trial is to evaluate the safety and reactogenicity of mRNA-1189 in 18- to 30-year-old healthy adults, the main objective of Part B is to evaluate the safety and reactogenicity of mRNA-1189 in 12- to <18-year-old healthy EBV-seronegative adolescents, and the main objective of Part C is to evaluate the safety and reactogenicity of mRNA-1189 in 10- to 21-year-old healthy adolescents and adults.

Inclusion Criteria:

• According to the assessment of the investigator, is in good general health and can comply with study procedures.

Part A: Healthy adult from 18 to 30 years of age (inclusive) at the time of consent (Screening Visit, Day 0).

Part B:

Healthy baseline EBV-seronegative adolescents from 12 to <18 years of age at the time of consent (Screening Visit, Day 0).

Part C:

Healthy adolescents and adults from 10 to 21 years of age (inclusive) at the time of consent (Screening Visit, Day 0).

Exclusion Criteria:

• Has had significant exposure to someone with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or COVID-19 in the past 14 days prior to the screening visit, if the participant has not been fully vaccinated against COVID-19 at least 14 days prior to the screening visit.
• Has 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).
• Significant, progressive, unstable or uncontrolled clinical condition, including any condition that may affect participant safety, assessment of study endpoints, assessment of immune response, or adherence to study procedures per investigator judgement.
• Has a history of myocarditis, and/or pericarditis.
• 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 vaccine injection, with the exception of licensed influenza vaccines, which may be received more than 14 days before or after any study vaccine injection.

Note: Other inclusion and exclusion criteria may apply.