Study to Evaluate the Efficacy, Immunogenicity, and Safety of RSVpreF in Adults.

Eligibility Criteria

• * Participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, frequent symptom assessment by mobile device application, and other study procedures, including collection of nasal swabs by themselves and by study staff when indicated.
• * Healthy participants who are determined by medical history, physical examination (if required), and clinical judgment of the investigator to be eligible for inclusion in the study.
• * Adults who are ambulatory and live in the community, or in assisted living or long-term care residential facilities that provide minimal assistance, such that the participant is primarily responsible for self-care and activities of daily living.
• * Capable of giving signed informed consent as described in the protocol, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol.
• * Male or female participants ≥60 years of age.
• * Male participants able to father children must agree to use a highly effective method of contraception from the time of informed consent through at least 28 days after study intervention administration.
• * Female participants must not be of childbearing potential.
• * Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
• * History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention(s) or any related vaccine.
• * Serious chronic disorder including metastatic malignancy, end-stage renal disease with or without dialysis, clinically unstable cardiac disease, or any other disorder that, in the investigator's opinion, excludes the participant from participating in the study.
• * Immunocompromised individuals with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination.
• * Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
• * Participation in other studies involving an investigational product within 28 days prior to consent and/or through and including the 6-months follow-up visit (Visit 3).
• * Receipt of blood/plasma products or immunoglobulin within 60 days before study intervention administration.
• * Previous vaccination with any licensed or investigational RSV vaccine or planned receipt during study participation.
• * Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members.