A Study to Evaluate the Efficacy and Safety of mRNA-1283 and mRNA-1273 in Participants 50 to 64 Years of Age Without High-Risk Conditions for Severe Coronavirus Disease 2019 (COVID-19)

Key Inclusion Criteria:

• Healthy and without underlying medical conditions that may put them at higher riskof experiencing severe outcomes of COVID-19, as determined by medical evaluationincluding medical history, physical examination, laboratory tests, and cardiacmonitoring.

Key Exclusion Criteria:

• History of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectionwithin 3 months prior to enrollment.

• Acutely ill or febrile within 72 hours prior to or at the Screening Visit or Day 1.

• Receipt of any of the following:

• COVID-19 vaccine within 3 months prior to enrollment,

• Any licensed non COVID-19 vaccine within 28 days before or planned receiptwithin 28 days after the study intervention, except an influenza vaccine, whichmay be given 14 days before or after receipt of the study intervention,

• Corticosteroids at ≥10 milligrams (mg)/day of prednisone or equivalent for >14days in total within 90 days prior to Day 1 or is anticipating the need forcorticosteroids at any time during the study or,

• Systemic immunosuppressive treatment within 180 days prior to the Screening oris anticipating the need for systemic immunosuppressive treatment at any timeduring participation in the study.

• Has donated ≥450 mL of blood products within 28 days prior to the Screening Visit orplans to donate blood products within 28 days post study injection.

• Has participated in an investigational clinical study within 28 days prior to theScreening Visit based on the medical history interview or plans to do so whileparticipating in this study.

Note: Additional inclusion/exclusion criteria may apply, per protocol.