A Study of mRNA-based Influenza and SARS-CoV-2 (COVID-19) Multi-component Vaccines in Healthy Adults

Part 1: Participants will be enrolled into 1 of 2 age cohorts: Cohort A for adults ≥65 to \<80 years of age or Cohort B for adults ≥18 to \<65 year of age. In Cohort A, approximately 600 participants will be randomized (in equal allocation ratio) into the investigational treatment arms, stratified by influenza vaccine status in the most recent influenza season (received or not received since September 2022). In Cohort B, approximately 624 participants will be randomized (in equal allocation ratio) into the investigational treatment arms, stratified by 2 age groups: ≥18 to \<50 years and ≥50 to \<65 years of age and by influenza vaccine status in the most recent influenza season (received or not received since September 2022). Part 2: Approximately, 520 participants between ≥18 to \<50 years of age will be randomized (in equal allocation ratio) into the investigational treatment arms, stratified by influenza vaccine status in the most recent influenza season (received or not received since Sept 2023).