A Study on the Immune Response and Safety of a Vaccine Against Respiratory Syncytial Virus (RSV) When Given Alone and Together With a COVID-19 mRNA Vaccine in Adults Aged 50 Years and Above

Inclusion Criteria

• Participants, who, in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g., completion of the diary cards, return for follow-up visits).

Note: In case of physical incapacity that would preclude the self-completion of the diary cards, either site staff can assist the participant (for activities performed during site visits) or the participant may assign a caregiver to assist him/her with this activity (for activities performed at home). However, at no time will the site staff or caregiver evaluate the participant's health status while answering diaries or make decisions on behalf of the participant.

• Written or witnessed informed consent obtained from the participant (participant must be able to understand the informed consent) prior to performance of any study-specific procedure.
• A male/female of ≥50 Years of age (YOA) at the time of the first study intervention administration.
• Participants who are medically stable in the opinion of the investigator at the time of first vaccination. 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.

A stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months before enrollment.

• 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.

Participants who have received previously a SARS-CoV-2 vaccine, being administered at least 3 months prior to study vaccination.

• Female participants of non-childbearing potential may be enrolled in the study. Non childbearing potential is defined as hysterectomy, bilateral oophorectomy, bilateral salpingectomy, and 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 and agreed to continue adequate contraception for at least 1 month after the last vaccination.
• has a negative pregnancy test on the day of and prior to study intervention administration.

Exclusion Criteria

Medical Conditions

• History of any reaction or hypersensitivity likely to be exacerbated by any component of the study interventions, including a known history of severe allergic reaction (e.g., anaphylaxis).
• Any confirmed or suspected immunosuppressive or immunodeficient condition, resulting from disease (e.g., current malignancy, human immunodeficiency virus) or immunosuppressive/cytotoxic therapy (e.g., medication used during cancer chemotherapy, organ transplantation, or to treat autoimmune disorders), based on medical history and physical examination (no laboratory testing required).
• Any history of myocarditis or pericarditis.
• Recurrent history 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 (e.g. completion of diary cards, attend regular phone calls/study site visits).
• Serious or unstable chronic illness.
• Any history of dementia or any medical condition that moderately or severely impairs cognition.
• Significant underlying illness that in the opinion of the investigator would be expected to prevent completion of the study (e.g., life-threatening disease likely to limit survival up to study end).
• Any medical condition that in the judgment of the investigator would make intramuscular injection unsafe.
• Any SAE attributed to a previous dose of the SARS-CoV-2 mRNA vaccine.
• Any other cli