Assess the Safety and Immunogenicity of NDV-HXP-S Vaccine in Thailand

Inclusion Criteria: Phase 1 Only: 1. Adult 18 through 59 years of age, inclusive, at screening 2. Healthy, as defined by absence of clinically significant medical condition, either acute or chronic, as determined by medical history, physical examination, screening laboratory test results, and clinical assessment of the investigator. Phase 2 Only: 1. Adult 18 through 75 years of age, inclusive, at screening. 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. Both Phase 1 and Phase 2: 1. Has provided written informed consent prior to performance of any study-specific procedure. 2. Has a body mass index (BMI) of 17 to 40 kg/m2, inclusive, at screening. 3. Resides in study site area and is able and willing to adhere to all protocol visits and procedures. 4. If a woman is of childbearing potential, must not be breastfeeding or be pregnant (based on a negative serum pregnancy test at screening and a negative urine pregnancy test 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: Phase 1 Only: 1\. A positive serologic test for SARS-CoV-2 IgG test. Both Phase 1 and Phase 2: 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 during the course of study participation Note: receipt of any COVID-19 vaccine that is licensed or granted Emergency Use Authorization in Thailand 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 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. 11. A positive serologic test for SARS-CoV-2 IgM test, human immunodeficiency virus (HIV 1/2 Ab), hepatitis B (HBsAg) or hepatitis C (HCV Ab) 12. History of laboratory-confirmed COVID-19 (RT-PCR positive to SAR-CoV-2) 13. History of malignancy, excluding non-melanoma skin and cervical carcinoma in situ 14. Any confirmed or suspected immunosuppressive or immunodeficient state 15. Administration of immunoglobulin or any blood product within 90 days prior to first study injection or planned administration during the study period. 16. 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). 17. History of known disturbance of coagulation or blood disorder that could cause anemia or excess bleeding. (e.g, thalassemia, coagulation factor deficiencies). 18. Recent history (within the past year) or signs of alcohol or substance abuse. 19. 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. 20. Employee of any person employed by the Sponsor, the contract research organization (CRO), the PI, study site personnel, or site. Note: specific exclusion criteria (e.g., ≥Grade 2 acute illness, or abnormal vital sign deemed clinically relevant by the PI) will be reassessed at both vaccination visits. Any subject who cannot be vaccinated due to an acute abnormality assessed at a vaccination visit (Visit 1 or Visit 3) may return once the acute issue has resolved, if deemed appropriate by the PI. A minimum of 48 hours must have passed after a documented fever before a subject can be vaccinated. This safety requirement will not be deemed a protocol deviation should the visit fall outside the vaccination window; however, it will be encouraged to maintain the vaccination window whenever possible in these situations. Clinical laboratory test results and vital signs used to determine subject eligibility will be those obtained at screening. These tests may be repeated once if deemed appropriate by the investigator and determined to be due to a transient condition that has resolved. In addition, a test may also be repeated for test results determined to be spurious by the investigator (e.g., following improper specimen collection). The last measurement will be taken as the baseline for purposes of analysis.