Systems Biological Analysis of Immune Responses to RSV Vaccine

Inclusion Criteria: * Adults ≥60 years of age at the time of enrollment. * Able and willing to provide written informed consent. * Eligible for receipt of an FDA-approved RSV vaccine (MRESVIA) per Advisory Committee on Immunization Practices (ACIP)/Centers for Disease Control and Prevention (CDC) guidelines. * Available for all study visits and procedures, including follow-up through Day 365. * Willing to allow access to prior RSV vaccination history (if applicable) for eligibility verification Exclusion Criteria: * History of severe allergic reaction (e.g., anaphylaxis) to any prior vaccines or any component of the MRESVIA vaccine, including polyethylene glycol (PEG), the amino lipid SM-102 (SM-102), or other listed excipients. * Acute illness or fever (temperature ≥100.4°F) at the time of vaccination (participant may be rescheduled). * Immunocompromising conditions, including: * Current cancer chemotherapy or immunosuppressive therapy. * History of hematologic malignancies or other immune-mediated diseases that would interfere with vaccine response. * Known or suspected HIV infection with cluster of differentiation 4 (CD4) count \<200 or uncontrolled viremia. * Clinically significant cardiac, pulmonary, renal, hepatic, or neurological disease that, in the opinion of the investigator, would preclude participation or confound interpretation of immune data. * Uncontrolled autoimmune disorder. * Current use of systemic corticosteroids equivalent to ≥20 mg prednisone d…