A Study on the Immune Response and Safety of a Vaccine Against Respiratory Syncytial Virus Given to Adults 50-59 Years of Age, Including Adults at Increased Risk of Respiratory Syncytial Virus Lower Respiratory Tract Disease, Compared to Older Adults 60 Years of Age and Above

Inclusion Criteria

• Participants who, in the opinion of the investigator, can and will comply with the requirements of the protocol
• Written or witnessed informed consent obtained from the participant prior to performance of any study-specific procedure.
• Specific inclusion criteria for all participants in Cohort 1 (Adults HA-RSV Group, Adults HA-Placebo Group, Adults AIR-RSV Group & Adults AIR-Placebo Group)
• A male or female participant 50-59 YOA at the time of the study intervention administration.
• Female participants of non-childbearing potential may be enrolled in the study. Non-childbearing potential is defined as hysterectomy, bilateral oophorectomy, bilateral salpingectomy or post-menopause.
• Female participants of childbearing potential may be enrolled in the study, if the participant:
• has practiced adequate contraception from 1 month prior to study intervention administration until study end for this study, and
• has a negative pregnancy test on the day of study intervention administration.

Specific inclusion criteria for participants in the Adults-HA Sub-cohort

• Healthy participants as established by medical history and clinical examination before entering into the study.
• Participants with chronic stable medical conditions with or without specific treatment, such as hypertension, hypercholesterolemia, or hypothyroidism, and who are not at increased risk for RSV-LRTD , are allowed to participate in this study if considered by the investigator as medically stable (no changes in the treatment or disease severity in the past 3 months).

Specific inclusion criteria for participants in the Adults-AIR Sub cohort

Participants should be diagnosed with at least 1 of the following medical conditions and have a stable condition (no changes in the treatment or disease severity in the past 3 months):

• Chronic pulmonary disease resulting in activity restricting symptoms or use of long-term medication
• Chronic cardiovascular disease
• Diabetes mellitus: types 1 and 2
• Other diseases at increased risk for RSV-LRTD disease
• Chronic kidney disease
• Chronic liver disease 2. Specific inclusion criteria for Cohort 2 (OA-RSV Group)
• A male or female participant ≥60 YOA at the time of the study intervention administration.
• 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 (no changes in the treatment or disease severity in the past 3 months).
• Participants living in the general community or in an assisted-living facility that provides minimal assistance, such that the participant is primarily responsible for self-care and activities of daily living.

Exclusion Criteria

Medical conditions

• Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease or immunosuppressive/cytotoxic therapy, based on medical history and physical examination (no laboratory testing required).
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the study intervention.
• Hypersensitivity to latex.
• Unstable chronic illness.
• Any history of dementia or any medical condition that moderately or severely impairs cognition.
• Recurrent or uncontrolled neurological disorders or seizures. Participants with medically controlled active or chronic neurological diseases can be enrolled in the study as per investigator assessment, provided that their condition will allow them to comply with the requirements of the protocol. Study participants may decide to assign a caregiver to help them complete the study procedures.
• Significant underlying illness that in the opinion of the investigator would be expected to prevent completion of the study.
• Any medical condition that in the judgment of the investigator would make intramuscular injection unsafe.

Prior/Concomitant therapy

• Use of a