A Study to Learn About the Safety and Immune Responses of RSVpreF in Older Adults

The purpose of this study is to learn about the safety, tolerability, and immune response of the RSVpreF vaccine in healthy older adults. Participants will take part in this study for about 6 months. The study will include people in China and the United States. In China, participants will receive either RSVpreF or placebo. A placebo is a dummy vaccine with no active ingredient, but it looks just like the vaccine being studied. In the United States, all participants will receive RSVpreF. Researchers will check for any reactions. They will also check blood test results to learn how the body responds to the vaccine. The main questions the study aims to answer are: * What local reactions and systemic events (body-wide symptoms) do participants have after a RSVpreF vaccination? * What medical problems do participants have after a RSVpreF vaccination? * Researchers will compare antibody levels from blood tests between the China cohort and the US cohort. An antibody is a substance in the body that try to fight off an infection or foreign substance. Participants will: * Have a screening visit to make sure they qualify for the study (participants in China will have this visit before the day of vaccination) * Receive the RSVpreF vaccination (or a placebo injection if in the China cohort) once at Visit 1. * Have a telephone or clinic visit 1 week later to assess local reactions and systemic events. * Have a clinic visit a month after vaccination for a checkup and tests. * Have a telephone or clinic visit 6 months after vaccination for a health check. * Have a blood test at screening (if in the China cohort only), on the day of vaccination and 1 month after vaccination.

Key Inclusion Criteria * Participants 60 years of age or older at enrolment. * Healthy participants, or participants with stable long-term medical conditions, if the investigator decides they can take part. * Adults who can walk and live in the community or in assisted-living/long-term care settings with minimal help. * Participants who can give signed informed consent and follow study visits and procedures, including the 7-day electronic diary and blood tests. Key Exclusion Criteria * Confirmed RSV infection 180 days or less before study vaccination. * Any past history of Guillain-Barré syndrome. * Severe reaction to a vaccine or severe allergy to a study vaccine component or related vaccine. * Serious or unstable medical condition that the investigator believes makes the study unsafe. * Immunocompromised status, based on medical history and/or examination. * Previous receipt of any licensed or investigational RSV vaccine or RSV preventive monoclonal antibody, or planned receipt during the study. Please refer to the study contact for further eligibility details Contacts/Locations Central Contact Person: Pfizer CT.gov Call Center Telephone: 1-800-718-1021 Email: ClinicalTrials.gov\_Inquiries@pfizer.com