A Study to Evaluate the Safety and Immunogenicity of an Adjuvanted RSV Vaccine in Healthy Older Adults

Inclusion Criteria: 1. Evidence of a personally signed and dated informed consent document (ICD) indicating that the subject has been informed of all pertinent aspects of the study. 2. Healthy adults who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. 3. Willing and able to comply with scheduled visits, vaccination plan, laboratory tests, and other study procedures. 4. Male and nonchildbearing-potential female adults aged 65 to 85 years at the time of enrollment (signing of the ICD). 5. Subjects must have received the primary vaccination (RSV vaccine or placebo) at Visit 1 and have signed and dated the ICD for participating in the revaccination stage (applies to Primary Study Cohort - Stage 2 subjects). Exclusion Criteria: 1. Investigator site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, or subjects who are Pfizer employees, including their family members, directly involved in the conduct of the study. 2. Participation in other studies involving investigational product within 28 days prior to study entry and/or during study participation. 3. Known infection with HIV, hepatitis C virus (HCV), or hepatitis B virus (HBV). 4. Previous vaccination with any licensed or investigational RSV vaccine before enrollment into the study, or planned receipt throughout the study of nonstudy RSV vaccine. 5. Vaccination with any influenza vaccine within 6 months (182 days) before investigational product administration (applies to Primary Study Cohort - Stages 1 and 2). 6. History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the investigational product(s), including natural rubber latex. In addition, a history of severe allergic reaction (eg, anaphylaxis) to any substance, including documented allergy to egg proteins (egg or egg products) or chicken proteins. 7. Subjects with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination. 8. Subjects who receive treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, eg, for cancer or an autoimmune disease, or planned receipt throughout the study. If systemic corticosteroids have been administered short term (\<14 days) for treatment of an acute illness, subjects should not be enrolled into the study until corticosteroid therapy has been discontinued for at least 28 days before investigational product administration.Inhaled/nebulized, intra-articular, intrabursal, or topical (epidural, skin or eyes) corticosteroids are permitted. 9. Subject with a history of autoimmune disease or an active autoimmune disease requiring therapeutic intervention including but not limited to: systemic or cutaneous lupus erythematosus, autoimmune arthritis/rheumatoid arthritis, Guillain-Barré syndrome,multiple sclerosis, Sjögren syndrome, idiopathic thrombocytopenic purpura, autoimmune glomerulonephritis, autoimmune thyroiditis, giant cell arteritis (temporal arteritis), psoriasis, and insulin-dependent diabetes mellitus (type 1). 10. Receipt of blood/plasma products or immunoglobulin, from 60 days before investigational product administration or planned receipt throughout the study. 11. Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection. 12. Female subjects of childbearing potential or who are pregnant or breastfeeding; fertile male subjects who are unwilling to use a highly effective method of contraception for at least 28 days after the last dose of investigational product. 13. Other acute or chronic medical or psychiatric condition including recent (within the past year) or active suicidal ideation or behavior or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the subject inappropriate for entry into this study. 14. Planned donation of blood volumes of approximately 470 mL within 12 weeks after Vaccination 1 (applies to subjects having additional blood drawn for cellular assays).