A Study to Characterize the Safety and Immunogenicity of AZD6489 in Participants 60 Years of Age and Older (ARIES)

Inclusion Criteria: * Participant must be ≥ 60 years of age at the time of signing the informed consent. * Participants who are medically stable in the opinion of the Investigator at the time of study intervention. Participants with chronic stable medical conditions with or without specific treatment, such as diabetes, hypertension, or cardiac disease, are allowed to participate in this study if considered by the Investigator as medically stable. * Able to understand and comply with study requirements/procedures including attending all scheduled study visits (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined) based on the assessment of the Investigator. * Capable of giving signed informed consent as described in Appendix A 3 which includes compliance with the requirements and restrictions listed in the ICF and in this protocol. Exclusion Criteria: * Previous known laboratory-confirmed RSV infection within 6 months of Visit 1. * Moderate to severe acute (time-limited) or any febrile (temperature ≥ 38.0 °C \[100.4 ºF\]) illness/infection within 3 days of Visit 1; participants excluded for transient acute illness may be rescreened once and vaccinated if the illness has resolved. * History of a clinically significant bleeding disorder contraindicating IM injections or venipuncture based on Investigator judgment. * History of hypersensitivity to any component of the study interventions. * History of severe adverse reaction or severe allergic reaction (eg, anaphylaxis) associated with any vaccine. * Known chronic hepatitis B or C. * Known or suspected congenital or acquired immunodeficiency. * History of Guillain-Barré syndrome or any other demyelinating condition. * Current or previous (within the past 5 years) history of any malignancy (except treated non-melanoma skin cancers, locally treated cervical cancer, or prostate cancer that is stable at the time of vaccination in the absence of therapy). * Chronic illness that, in the opinion of the Investigator, is at a stage where it might interfere with study conduct or completion. * Receipt of any licensed or investigational RSV vaccine within 2 years prior to Visit 1, or planned receipt during the study. * Receipt of any licensed vaccine (including licensed influenza or COVID-19 vaccines) within 28 days prior to Visit 1 or expected receipt prior to end of Visit 3 assessments. * Receipt of immunoglobulin or blood products within 3 months prior to Visit 1, or planned receipt during the study. * Receipt of immune-modifying drugs or immunosuppressive therapy (eg, anti-cancer chemotherapy, anti-cytokine therapy, or radiation therapy) within 6 months prior to Visit 1, or planned receipt during study. * Long-term systemic corticosteroid therapy (prednisone or equivalent at a dose of ≥ 20 mg daily or every other day for more than 2 consecutive weeks) within 6 months prior to Visit 1 or planned receipt during study. Topical/inhaled/intra-articular/ophthalmic/otic steroids or short-term oral steroids are permitted. * Receipt of allergen immunotherapy if dose has been escalated or reduced within 30 days of Visit 1. Allergen immunotherapy is allowed if participant is receiving stable desensitization therapy for at least 30 days prior to Visit 1 and there is no anticipated change before Visit 3. * Participation in another clinical study with a study intervention administered in the preceding 90 days (or preceding 6 months for extended half-life drug products) or expected receipt of another study intervention during the study, or concurrent participation in another interventional study. Individuals who are in a prolonged post-administration observation period of another investigational, marketed drug, or non-interventional clinical study, for which there is no ongoing exposure to the investigational or marketed product and all scheduled on-site visits are completed, will be allowed to take part in this study, if all other eligibility criteria are met.