A Study of mRNA-1345 Following a Primary Dose of a Licensed Protein Subunit Respiratory Syncytial Virus (RSV) Vaccine in Adult Participants ≥60 Years of Age

Key Inclusion Criteria:

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

• Absence of changes in medical therapy within 60 days of Visit 1 due totreatment failure or toxicity.

• Absence of serious or significant medical events within 30 days of Visit 1.

• Absence of known, current, and life-limiting diagnoses which, in the opinion ofthe Investigator, would make completion of the protocol unlikely.

• Participant has received a single dose of Arexvy or Abrysvo at least 12 months priorto Visit 1. Participants must provide proof of RSV vaccination status (includingbrand and date received) prior to enrollment.

Key Exclusion Criteria:

• Participant has received or plans to receive any vaccine authorized or approved by alocal health agency ≤14 days prior to study injection (Day 1) or plans to receive avaccine authorized or approved by a local health agency within 14 days after thestudy injection. Nonstudy vaccination(s) should not be delayed.

• Prior participation in research involving receipt of any investigational RSV product (drug/biologic).

• Has received systemic immunoglobulins, long-acting biological therapies that affectimmune responses (for example, infliximab) or blood products within 90 days prior toVisit 1 or plans to receive them during the study.

Other protocol-specified inclusion and/or exclusion criteria may apply.