The purpose of this phase 3 multicenter, double-blinded, placebo-controlled study in India is to learn about the safety and immunogenicity of RSVpreF in adults.

Key Inclusion Criteria:

• Participants ≥18 years of age at Visit 1.
• Participants who are ambulatory and live independently in the community.
• Participants who are determined by medical history, physical examination (if required), and clinical judgment of the investigator to be eligible for inclusion in the study.
• Applicable to participants 18 through 59 years of age: Participants who are healthy or have stable preexisting diseases. These participants are considered at high risk of RSV disease by having at least 1 reportable stable chronic medical condition(s) that belongs to 1 or more of the following:
• Chronic heart disease (ie, coronary artery disease, heart failure, or congenital heart disease)
• Chronic lung disease (ie, COPD, emphysema, asthma, interstitial lung disease, or cystic fibrosis)
• Nongestational diabetes mellitus type 1 or type 2
• Severe obesity (body mass index [BMI] ≥40 kg/m2)
• Chronic liver disease (ie, cirrhosis)
• Chronic kidney disease (not including end-stage renal disease with or without dialysis)
• Chronic neurological disease that causes impaired airway clearance or respiratory muscle weakness (ie, poststroke dysphagia, amyotrophic lateral sclerosis, or muscular dystrophy)
• Chronic hematologic disease (ie, sickle cell disease or thalassemia)

Note: A chronic medical condition for this study is defined as:

• Duration ≥6 months.
• Requires regular medical follow-up or ongoing prescribed medication or hospitalization in the previous year.
• Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent document (ICD) and in the protocol.

Key Exclusion Criteria:

• Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
• History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention(s) or any related vaccine.
• Prior history of any subtype of Guillain-Barré syndrome of any etiology.
• Serious chronic disorder, including metastatic malignancy, end-stage renal disease with or without dialysis, clinically unstable cardiac disease, or any other disorder that, in the investigator's opinion, excludes the participant from participating in the study.
• Immunocompromised individuals with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination.
• Individuals who receive chronic systemic treatment with immunosuppressive therapy, including cytotoxic agents, immunosuppressive monoclonal antibodies, systemic corticosteroids, or radiotherapy, eg, for cancer or an autoimmune disease, from 60 days before study intervention administration or planned receipt throughout the study.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Double-blinded, placebo-controlled.