A Study to Assess the Safety, Reactogenicity, and Immunogenicity of SK Japanese Encephalitis Messenger Ribonucleic Acid (mRNA) Vaccines (GBP560) in Healthy Adults

Inclusion Criteria:

[Age]

1. For Stage 1, participant must be 18 to 55 years of age inclusive, at the time ofsigning the informed consent. For Stage 2, participant must be 18 years of age and older, at the time of signingthe informed consent.

[Type of Participant and Disease Characteristics]

2. Participants who are healthy as determined by medical evaluation including medicalhistory, vital signs, physical examination, clinical laboratory tests and medicaljudgement of the investigator.

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

4. Body mass index (BMI) within the range of 18.5-29.9 kg/m2 (inclusive) at screening

[Sex and Contraceptive/Barrier Requirements]

5. All participants must agree to be heterosexually inactive or agree to consistentlyuse at least one acceptable method of contraception from at least 4 weeks prior tothe 1st study vaccination to 12 weeks after the last study vaccination (Visit 9) (See Appendix 10.4 for detailed contraceptive methods).

6. Female participants with a negative urine or serum pregnancy test at screening.

• Female participants who are surgically sterile (e.g., having undergone a fullhysterectomy, bilateral salpingectomy, or bilateral oophorectomy) or postmenopausalwith amenorrhea for at least 12 months are not subject to a pregnancy test.

[Informed Consent]

7. Participants who are capable of giving signed informed consent as described inAppendix 10.1.3 which includes compliance with the requirements and restrictionslisted in the informed consent form (ICF) and in this protocol before initiation ofany trial-specific procedures.

Exclusion Criteria:

[Medical Conditions]

1. Any clinically significant respiratory symptoms (e.g., cough, sore throat), febrileillness (tympanic temperature >38°C), or acute illness within 24 hours prior to the 1st study vaccination. Prospective participants with these conditions cannot beincluded until 24 hours after resolution.

2. History of congenital, hereditary, acquired immunodeficiency, or autoimmune disease.

3. Any positive test results for hepatitis B surface antigen, hepatitis C antibody, orhuman immunodeficiency virus (HIV) at screening.

4. History of bleeding disorder or thrombocytopenia which is contraindicatingintramuscular vaccination in the investigator's opinion.

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

6. History of myocarditis, pericarditis or myopericarditis (including the screening 12-lead ECG results from Stage 1 participants), as assessed by the investigator,indicating probable or possible myocarditis, pericarditis, or myopericarditis, ordemonstrating clinically significant abnormalities that could affect participantsafety or the interpretation of study findings.

7. History of JEV infection/other flaviviruses infection (e.g., Dengue, West Nile,Zika, St. Louis Encephalitis, Yellow fever).

8. History of malignancy within 1 year prior to the 1st study vaccination (with theexception of malignancy with minimal risk of recurrence at the discretion of theinvestigator).

9. Significant unstable chronic or acute illness that, in the opinion of theinvestigator, might pose a health risk to the participant if enrolled, or couldinterfere with the protocol-specified activities, or interpretation of studyresults.

• The AESIs as outlined in Section 8.1.4 should be considered for evaluating theparticipant

10. Any other conditions which, in the opinion of the investigator, might interfere withthe evaluation of the study objectives (e.g., alcohol or drug abuse, neurologic orpsychiatric conditions).

11. Female participants who are pregnant or breastfeeding.

12. (Only for Stage 1) Current smoker or a recent smoking history within 12 weeks priorto screening. Occasional smoker who smokes up to 10 cigarettes per month may beallowed to participate at the investigator's discretion.

[Prior/Concomitant medication]

13. Receipt of JEV vaccination/other flaviviruses vaccination in the past.

14. Receipt of any vaccine within 4 weeks prior to the 1st study vaccination or plannedreceipt of any vaccine from enrollment through 4 weeks after the last studyvaccination (Visit 8), except for inactivated influenza vaccination, which may bereceived at least 2 weeks prior to the 1st study vaccination.

15. Receipt of immunoglobulins and/or any blood or blood-derived products within 12weeks prior to the 1st study vaccination.

16. Receipt of immunosuppressive therapy, such as any use of anti-cancer chemotherapy orradiation therapy; or systemic corticosteroid therapy (≥10 mg prednisone/day orequivalent) within 12 weeks prior to the 1st study vaccination. The use of inhaled,topical, or nasal glucocorticoid will be permitted.

[Prior/Concurrent Clinical Study Experience]

17. Participation in another clinical study and receipt of study intervention within 4weeks prior to the 1st study vaccination, or concurrent, planned participation inanother clinical study with study intervention during this study period.

[Other Exclusions]

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

19. Donation of ≥ 450mL (milliliter) of blood product within 4 weeks prior to screening,or planned donation of blood product from enrollment through 12 weeks after the laststudy vaccination (Visit 9).