Inclusion Criteria:

1. Adults aged 65 or older at Day 0.

2. Are willing and able to sign the informed consent and can comply with all study
visits and procedures.

3. Participant must have received at least a primary scheme of an mRNA vaccine (2
doses). Booster doses or previous COVID-19 infections are allowed. Last dose must
have been administered at least 6 months before Day 0. History of COVID-19 infection
is allowed if occurred at least >30 days before Day 0.

4. Have a negative Rapid Antigen Test (RAT) at Day 0 before vaccinations.

5. Adults determined by clinical assessment, including medical history and clinical
judgement, to be eligible for the study, including adults with pre-existing chronic
and stable diseases (non-immunocompromised), if these are stable and well-controlled
according to the investigator's judgment.

Exclusion Criteria:

6. Acute illness with fever ≥ 38.0°C at Day 0 or within 24 hours prior to vaccination.
Afebrile participants with minor illnesses can be enrolled at the discretion of the
investigator.

7. Allergy to egg proteins (egg or egg products) or chicken proteins.

8. History of Guillain-Barré syndrome (GBS)

9. History of COVID-19 infection (described as a positive RAT or PCR), in the previous
30 days before Day 0.

10. Other medical or psychiatric condition including recent (within the past year) or
active suicidal ideation/behaviour that may increase the risk of study participation
or, in the investigator's judgment, make the participant inappropriate for the
study.

11. History of severe adverse reaction associated with a vaccine and/or severe allergic
reaction (e.g. anaphylaxis) to any component of the study intervention(s).

12. Immunocompromised individuals defined as those with primary and secondary immune
deficiencies and those receiving chemotherapy or immunosuppressant drugs other than
steroids and glucocorticoids (maximum 30mg/day of prednisone, or equivalent, by any
administration route for a maximum of 30 consecutive days), within 90 days prior to
vaccination or during the study.

13. Bleeding diathesis or condition associated with prolonged bleeding that would, in
the opinion of the investigator, contraindicate intramuscular injection.

14. Receipt of blood-derived immune globulins, blood, or blood-derived products in the
past 3 months.

15. Participation in other studies involving study intervention within 28 days prior to
screening and/or during study participation.

16. Received any non-study vaccine within 14 days before or after screening. For live or
attenuated vaccines, 4 weeks before or after screening.

17. History of a diagnosis or other conditions that, in the judgment of the
investigator, may affect study endpoint assessment or compromise participant safety.