A Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of mRNA-1468 in Healthy Adults ≥50 Years of Age

• Part 1: Is an adult 50 years of age or older at the time of consent. Part 2: Is an adult 50-69 years of age at the time of consent.
• Has a body mass index of 18 to <40 kilograms/meter squared at the Screening Visit.
• Females of childbearing potential: have a negative pregnancy test at the Screening Visit and on the day of the first vaccination (Day 1); have practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to Day 1; have agreed to continue adequate contraception through 3 months following vaccine administration; are not currently breastfeeding.

• Has a history of HZ within the past 10 years.
• Has been previously vaccinated against varicella or HZ.
• Is acutely ill or febrile
• Body temperature ≥38.0°Celsius/100.4°Fahrenheit 72 hours prior to or at the Screening Visit or on Day 1. Participants meeting this criterion may be rescheduled within the allowed window.
• Has a current or previous diagnosis of congenital or acquired immunodeficiency, immunocompromizing/immunosuppressive condition, asplenia, or recurrent severe infections. Certain immune-mediated conditions that are well controlled and stable (for example, Hashimoto thyroiditis) as well as those that do not require systemic immunosuppressive therapy (for example, asthma, psoriasis, or vitiligo) may be permitted at the discretion of the Investigator.
• Has a dermatologic condition that could affect local solicited adverse reaction assessments (for example, tattoos, psoriasis patches affecting skin over the deltoid areas).
• Has any medical, psychiatric, or occupational condition, including reported history of substance 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.
• Has a history of myocarditis, pericarditis, or myopericarditis.
• Has a reported history of anaphylaxis or severe hypersensitivity reaction after receipt of any mRNA vaccine(s) or any components of the mRNA vaccines.
• Has received systemic immunosuppressants for >14 days in total within 180 days prior to Screening Visit (for corticosteroids ≥10 milligrams/day of prednisone or equivalent) or is anticipating the need for systemic immunosuppressive treatment at any time during participation in the study. Inhaled, nasal, intra-articular and topical steroids are allowed.
• Has received systemic immunoglobulins, long-acting biological therapies that affect immune responses (for example, Infliximab) or blood products within 90 days prior to the Screening Visit or plans to receive them during the study.

Other protocol-defined inclusion/exclusion criteria apply.