A Study to Evaluate the Safety and Immune Response of mRNA-1345, a Vaccine Targeting Respiratory Syncytial Virus (RSV), When Co-administered With a Fluzone HD, in Adults ≥65 Years of Age

A Phase 3, Randomized, Observer-Blind Study to Evaluate Safety, Tolerability, and Immunogenicity of mRNA-1345, an mRNA Vaccine Targeting Respiratory Syncytial Virus, When Coadministered With a High-Dose, Quadrivalent Seasonal Influenza Vaccine in Adults ≥65 Years of Age

The main purpose of this study is to evaluate the safety and immunogenicity of mRNA-1345 RSV vaccine when coadministered with a high dose (HD) quadrivalent seasonal influenza vaccine (Fluzone HD) in adults ≥65 years of age. The study will examine the impact of Fluzone HD on the immune response to mRNA-1345 against RSV-A and RSV-B, as well as the impact of mRNA-1345 on the immune response to Fluzone HD against 4 vaccine-matched Influenza A and B strains.

Key Inclusion Criteria:

• Participants may have one or more chronic medical diagnoses, but should be medically stable as assessed by:

  • Absence of changes in medical therapy within 60 days of Day 1 due to treatment failure or toxicity,
  • Absence of serious or significant medical events within 30 days of Day 1, and
  • Absence of known, current, and life-limiting diagnoses which, in the opinion of the Investigator, would make completion of the protocol unlikely.

• A participant assigned female at birth is eligible to participate if they are postmenopausal or not a person of childbearing potential.

Key Exclusion Criteria:

• Close contact with someone with laboratory-confirmed influenza and/or RSV infection or with someone who has been treated with antiviral therapies for influenza (for example, Tamiflu®) within the past 5 days prior to Day 1.
• Reported history of congenital or acquired immunodeficiency, immunosuppressive condition or immune-mediated disease, asplenia, or recurrent severe infections.
• Participant has tested positive for influenza or RSV by local health authority-approved testing methods ≤6 months prior to Day 1.
• Participant has received or plans to receive any vaccine authorized or approved by a local health agency ≤28 days prior to study injections (Day 1 and Day 22) or plans to receive a vaccine authorized or approved by a local health agency within 28 days after study injections.
• Participant has received a seasonal influenza vaccine or any other investigational influenza vaccine ≤6 months prior to Day 1.
• Participant has received any RSV vaccine (authorized/approved by local health agency or investigational) prior to Day 1.

Note: Other protocol-defined inclusion and/or exclusion criteria may apply.