NDV-HXP-S Vaccine Clinical Trial (COVIVAC)

Inclusion Criteria: 1. Adult ≥ 18 years old inclusive at the time of randomization. 2. Having no clinically significant acute medical condition, and no chronic medical condition that has not been controlled within 90 days of randomization, as determined by medical history, physical examination, screening laboratory test results, and clinical assessment of the investigator. 3. Has provided written informed consent prior to performance of any study-specific procedure. 4. Has a body mass index (BMI) of 17 to 40 kg/m2, inclusive, at screening. 5. Resides in study site area and is able and willing to adhere to all protocol visits and procedures. 6. If a woman is of childbearing potential age, must not be breastfeeding or be pregnant (based on a negative urine pregnancy test at screening and during the 24 hours prior to receipt of the first dose of IP), must plan to avoid pregnancy for at least 28 days after the last dose of IP, and be willing to use an adequate method of contraception consistently and have a repeated pregnancy test prior to the second (last) dose of IP. Exclusion Criteria: 1. Use of any investigational medicinal product within 90 days prior to randomization or planned use of such a product during the period of study participation. 2. History of administration of any non-study vaccine within 28 days prior to administration of study vaccine or planned vaccination within 3 months after enrolment. Note: receipt of any COVID-19 vaccine that is licensed or granted Emergency Use Authorization in Vietnam during the course of study participation is not exclusionary if administered after Visit 5. 3. Previous receipt of investigational vaccine for SARS or MERS, or any investigational or licensed vaccine that may have an impact on interpretation of the trial results 4. History of hypersensitivity reaction to any prior vaccination or known hypersensitivity to any component of the study vaccine 5. History of egg or chicken allergy 6. History of angioedema 7. History of anaphylaxis (≥ grade 2) 8. Acute illness (moderate or severe) and/or fever (body temperature measured orally ≥38°C) 9. Any abnormal vital sign deemed clinically relevant by the PI 10. Abnormality in screening laboratory test deemed exclusionary by the PI in consultation with the Sponsor 11. A positive serologic test for hepatitis B (HBsAg) or hepatitis C (HCV Ab) (phase 1 only) 12. History of confirmed HIV 13. History of laboratory-confirmed COVID-19 14. History of malignancy, excluding non-melanoma skin and cervical carcinoma in situ 15. Any confirmed or suspected immunosuppressive or immunodeficient state 16. Administration of immunoglobulin or any blood product within 90 days prior to first study injection or planned administration during the study period. 17. Administration of any long-acting immune-modifying drugs (e.g., infliximab or rituximab) or the chronic administration (defined as more than 14 days) of immunosuppressants within six months prior to first study injection, or planned administration during the study period (includes systemic corticosteroids at doses equivalent to ≥ 0.5 mg/kg/day of prednisone; the use of topical steroids including inhaled and intranasal steroids is permitted). 18. History of known disturbance of coagulation or blood disorder that could cause anemia or excess bleeding. (e.g, thalassemia, coagulation factor deficiencies). 19. Recent history (within the past year) or signs of alcohol or substance abuse. 20. Any medical, psychiatric or behavior condition that in the opinion of the PI may interfere with the study objectives, pose a risk to the subject, or prevent the subject from completing the study follow-up. 21. Employee of any person employed by the Sponsor, the contract research organization (CRO), the PI, study site personnel, or site.