Inclusion Criteria:

1. Participant must be aged 19 years and older at the time of signing the informed
consent.

2. Participants who are healthy or medically stabilized according to medical judgment
of the investigator based on medical history, physical examination and clinical
laboratory tests, etc.

3. Participants who are able to attend all scheduled visits and comply with all study
procedures.

4. (Cohort 1~5) Participants who received a primary series of COVID-19 vaccination
approved for use in Korea by MFDS and at least 12~24 weeks have passed with no
additional COVID-19 vaccination.

5. (Cohort 6~7) Participants who received a primary series of COVID-19 vaccination and
the 1st booster vaccination at least 16 weeks ago through a homologous or
heterologous vaccination with mRNA vaccines (BNT162b2 (Pfizer) and mRNA-1273
(Moderna)) only or at least more than a single dose of non-mRNA vaccines (ChAdOx1
nCOV-19 (AZ), Ad26.COV2.S (Janssen), and NVX-CoV2373 (Novavax)).

6. Female participants of childbearing potential must agree to be heterosexually
inactive, or agree to use at least one acceptable method of contraception from at
least 4 weeks prior to the study vaccination (booster vaccination) to 12 weeks after
the study vaccination.

7. Female participants with a negative urine or serum pregnancy test at screening
(However, female participants who are surgically sterile or postmenopausal with
amenorrhea for at least 12 months shall be excluded.

8. Participants who give signed informed consent which include compliance with the
requirements and restrictions listed in the informed consent form and in the
protocol.

Exclusion Criteria:

1. Any clinically significant respiratory symptoms (e.g. cough, sore throat), febrile
illness (temperature >38°C), or acute illness within 72 hours prior to the study
vaccination (A prospective participant should not be included until 72 hours after
the condition has resolved).

2. History of virologically-confirmed COVID-19, SARS or MERS disease.

3. History of confirmed SARS-CoV-2 infection within three months before screening.

4. History of congenital or acquired immunodeficiency or autoimmune disease.

5. History of bleeding disorder including thrombocytopenia which is judged by the
investigator as a contraindication for intramuscular vaccination.

6. History of hypersensitivity and severe allergic reaction (e.g. anaphylaxis,
Guillain-Barre syndrome) to any components of the study intervention.

7. History of malignancy within 1 year prior to the study vaccination (Except for a
participant judged by the investigator to have a low recurrence risk.)

8. Any other clinically significant conditions such as uncontrollable chronic or acute
diseases which, in the opinion of the investigator, might cause a health threat to
the participant or interfere with the clinical trial procedures or interpretation of
the study results.

9. Any other conditions which might interfere with the evaluation of the study
objectives (e.g. alcohol or drug abuse, neurologic or psychiatric conditions).

10. Female participants who are pregnant or breastfeeding.

11. History of drug administration other than COVID-19 vaccination intended to treat or
prevent COVID-19.

12. History or planned other vaccination within 4 weeks prior to the study vaccination
through 28 days after the study vaccination (except for influenza vaccination, which
may be received at least 2 weeks prior to the study vaccination).

13. Receipt of immunoglobulins, whole blood or blood products within 12 weeks prior to
the study vaccination.

14. Use of immunosuppressive therapy such as anti-cancer chemotherapy or radiation
therapy for at least 2 consecutive weeks within 12 weeks prior to the study
vaccination or long-term systemic corticosteroid therapy (e.g. ≥10mg prednisone/day
or equivalent for more than 2 consecutive weeks) (However, the use of topical and
nasal glucocorticoids will be permitted.)

15. History of participation in another clinical study within 4 weeks prior to the study
vaccination or planned participation in another clinical study during this study
period.

16. Investigators, study staff who are directly involved in the conduct of this study or
supervised by the investigator, or their family members.