To Evaluate Safety and Immunogenicity of a Prophylactic Plasmid DNA

Phase 1 is the randomized, observer-blinded, multi-center, dose-finding part of the study, followed by an adaptive Phase 2 in which the optimal dose, determined from Phase 1, will be evaluated for safety and efficacy. In Phase 1 up to 50 participants are planned to be randomized 1:1 into one of two groups: either 100 μg intramuscular (IM) injection or 250 μg IM injection. Participants are to receive a single 0.5 mL IM injection of VAX-002 100 μg or 250 μg on Day 0. Follow-up visits will occur on Days 7, 14, 17 (phone call visit), 21, 28, 42, and 180. An interim analysis is planned once all participants in Phase 1 have completed their Day 28 visit to evaluate dose-response and safety to support optimal dose selection for Phase 2.

In Phase 2 approximately 250 participants will be enrolled and will receive a single 0.5 mL IM

injection of the optimal VAX-002 dose (determined in the Phase 1 interim analysis) on Day 0. Follow- up visits will occur on Days 7, 14, 17 (phone call visit), 21, 28, 42, and 180.

Inclusion criteria

• 1. Generally healthy adults aged 18 years or older at the time of enrollment and with a body mass index (BMI) of ≤30 kg/m2

• Completion of a prior COVID-19 primary vaccination course or booster (any commercially available within the study country) at least 3 months prior to enrollment OR recent clinically documented SARS-CoV-2 infection (by polymerase chain reaction [PCR] or antibody test) in the past three months but not within one month from enrollment.
• Willing to refrain from receiving an authorized COVID-19 booster dose until at least 90 days post IP administration.
• Female participants of child-bearing potential must have practiced adequate contraception for 30 days before IP injection, have a negative pregnancy test on the day of IP injection, and agree to continue adequate contraception until 180 days after IP injection. (Please refer to Section 10.44 for the definition of childbearing potential and adequate contraception).
• Male participants must agree to continue adequate contraception until 180 days after IP injection.
• Able to consent to participate in the study and signed an Informed Consent Form (ICF).
• Able and willing to complete all the scheduled study procedures during the whole study period (approximately 6.5 months).
• Generally, in good health, as determined by a review of medical history and a physical examination within 14 days prior to IP injection.

Exclusion criteria

• 1. History of anaphylaxis to key ingredients within the vaccine. 2. History of seizure disorder, encephalopathy, or psychosis. 3. Female participant is pregnant (positive urine pregnancy test), lactating, or plans to become pregnant during the 180 days of enrollment. 4. Positive test result for human immunodeficiency virus (HIV) or hepatitis B and C at Screening (test to be performed at the discretion of the investigator based on medical history or physical examination). 5. Positive result of lateral flow test for SARS-COV-2 on Day 0. 6. Laboratory (hematological and biochemistry) examination that is out of normal range or greater than a Grade 2 abnormality. Grade 1 abnormalities will not be exclusionary if considered not clinically significant by the investigator. Laboratory tests include: complete blood count (CBC), prothrombin time (PT), partial thromboplastin time (PTT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total bilirubin (T Bil), creatinine (CR), lipase, and blood glucose at screening. 7. Transient mild laboratory abnormalities may be rescreened once, and the participant will be excluded if the laboratory repeat test is abnormal as per local laboratory normal values and the investigator's assessment. 8. Presents with any acute febrile disease (oral temperature ≥37.5°C [99.5oF]) or active infectious disease within 48 hours prior to IP injection. 9. Unstable concomitant underlying conditions. Note: Stable condition defined as: the participant is appropriately managed on consistent disease management; for example, participants with well-controlled hypertension, adult-onset diabetes, benign prostate hypertrophy, or hypothyroid disease will be eligible for enrollment. The treatment regimen should be stable for at least 3 months prior to entering the study. Once IP treatment has started, the patient must be willing to maintain all aspects of the treatment regimen and forgo any elective changes in medication or management. Emergency changes in medication or management would be captured as an AE. 10. History of Guillain-Barre Syndrome or degenerative neurological disorders; a history of autoimmune, inflammatory disease or potential immune-mediated diseases (pIMD), or any condition that may put the participant at increased risk of safety events. 11. History of serious cardiovascular diseases, such as arrhythmia, conduction block, history of myocardial infarction, and severe hypertension not controlled with medication. 12. History of immunodeficiency, asplenia, or functional asplenia. 13. History of platelet disorder or other bleeding disorder that may cause contraindication for IM injection. 14. Heavy smoker (>10 cigarettes per day), vaper (>1 mL of e-liquid per day), or cannabis user ([near] daily use). Smokers have to agree to use the same cigarette brand throughout the study.

• History or diagnosis of coagulopathies. 16. Prior receipt of immunosuppressive medication, cytotoxic therapy, or systemic corticosteroids within 6 months before Day 0. 17. Recent receipt of blood products within 4 months before Day 0. 18. Administration of other investigational drugs within 3 months before Day 0 or planned use during the study period. 19. Currently has or a history of any condition that, in the opinion of the investigator, may interfere with the participant's compliance, evaluation of study objectives, or informed consent process (i.e., medical, psychological, social, or other conditions).