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 clinical condition that, in the opinion of the investigator, might pose
additional risk to the participant due to participation in the study.

- Recent SARS-CoV-2 infection within 3 months prior to the COVID-19 vaccine dose
administration. Timelines to be determined from symptoms onset or positive COVID-19
test (if infection was asymptomatic).

Prior/Concomitant Therapy Use of any investigational or non-registered product (drug,
vaccine or invasive medical device) other than the study interventions during the period
beginning 30 days before the first dose of study interventions and ending 30 days after
the last vaccine administration, or their planned use during the study period.

- Planned administration of a vaccine in the period starting 30 days before the first
dose and ending 30 days after the last dose of study intervention(s)
administration*, with the exception of inactivated and subunit influenza vaccines
which can be administered up to 14 days before or from 14 days after the study
vaccination.

*If emergency mass vaccination for an unforeseen public health threat (e.g., a
pandemic) is recommended and/or organized by public health authorities outside the
routine immunization program, the time period described above can be reduced if
necessary for that vaccine, provided it is used according to the local governmental
recommendations and Sponsor is notified.

- Chronic administration of immune-modifying drugs (defined as more than 14
consecutive days in total) and/or planned use of long-acting immune-modifying
treatments at any time up to the last blood sampling visit.

- Up to 3 months prior to the study intervention administration:

- For corticosteroids, this will mean prednisone equivalent ≥ 20 mg/day.
Inhaled and topical steroids are allowed.

- Administration of immunoglobulins and/or any blood products or plasma
derivatives.

- Up to 6 months prior to study intervention administration: long-acting immune
modifying drugs including among others immunotherapy (e.g., TNF-inhibitors),
monoclonal antibodies and antitumoral medication.

- Administration of any SARS-CoV-2 vaccine during the 3 months preceding the study
COVID-19 mRNA vaccine administration.

- Previous vaccination with licensed or investigational RSV vaccine. Prior/Concurrent
Clinical Study Experience

- Concurrently participating in another clinical study, at any time during the study
period, in which the participant has been or will be exposed to an investigational
or a non-investigational intervention (drug/invasive medical device).

Other Exclusion Criteria

- Pregnant or lactating female participant.

- Female participant planning to become pregnant or planning to discontinue
contraceptive precautions.

- History of chronic alcohol consumption and/or drug abuse as deemed by the
investigator to render the potential participant unable/unlikely to provide accurate
safety reports or comply with study procedures.

- Participation of any study personnel or their immediate dependents, family, or
household members.

- Planned move during the study conduct that prohibits participation until study end.

- Bedridden participants.