A Study to Evaluate the Efficacy of an RSV F Vaccine in Older Adults

Inclusion Criteria: 1. Males and females ≥60 years of age 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 subject is primarily responsible for self-care and activities of daily living. Subjects may have one or more chronic medical diagnoses, but should be clinically stable as assessed by: * Absence of changes in medical therapy within one month due to treatment failure or toxicity, * Absence of medical events qualifying as SAEs within one month of the planned vaccination on Day 0, and * Absence of known, current, and life-limiting diagnoses which, in the opinion of the investigator, render survival to completion of the protocol unlikely. 2. Willing and able (on both a physical and cognitive basis) to give informed consent prior to study enrollment. 3. Able to comply with study requirements; including access to transportation for study visits. 4. Access to inbound and outbound telephone communication with caregivers and study staff. Exclusion Criteria: 1. Participation in research involving investigational product (drug / biologic / device) within 45 days before the planned date of the Day 0 vaccination. 2. History of a serious reaction to any prior vaccination, or Guillain-Barré syndrome (GBS) within 6 weeks of any prior influenza immunization. 3. Receipt of any vaccine other than an IIV in the 4 weeks preceding the study vaccination or a pneumococcal vaccine in the 2 weeks preceding the study vaccination; or any RSV vaccine at any time. 4. Any known or suspected immunosuppressive condition, acquired or congenital, as determined by history and/or physical examination. 5. Chronic administration (defined as more than 14 continuous days) of immunosuppressants or other immune-modifying drugs within 6 months prior to the administration of the study vaccine. An immunosuppressant dose of glucocorticoid will be defined as a systemic dose ≥10mg of prednisone per day or equivalent. The use of topical, inhaled, and nasal glucocorticoids will be permitted. 6. Administration of immunoglobulins and/or any blood products within the 3 months preceding the administration of the study vaccine or during the study. 7. Acute disease at the time of enrollment (defined as the presence of a moderate or severe illness with or without fever, or an oral temperature ≥38.0°C on the planned day of vaccine administration). 8. Known uncontrolled disorder of coagulation. Potential subjects receiving aspirin, clopidogrel, prasugrel, dipyridamole, dabigatran, apixaban, rivaroxaban or warfarin under good control for cardiovascular prophylaxis or prophylaxis of thromboembolic disease or stroke in the setting of atrial fibrillation will NOT be excluded. 9. Suspicion or recent history (within one year of planned vaccination) of alcohol or other substance abuse. 10. Any condition that in the opinion of the investigator would pose a health risk to the subject if enrolled or could interfere with evaluation of the vaccine or interpretation of study results (including neurologic, cognitive, or psychiatric conditions deemed likely to impair the quality of study compliance or safety reporting).