This study is a phase 1, open-label, randomized, first-in-human clinical trial to evaluate the safety, tolerability and reactogenicity of escalating doses of Baiya SARS-CoV-2 VAX1 vaccine in participants aged 18-60 for adult groups and 61-75 for elderly groups. Each group will consist of three cohorts to evaluate different doses (low, medium, high) of Baiya SARS-CoV-2 VAX vaccine. Participants will be injected with two doses of the investigational product with a 21-day interval.

Inclusion Criteria:

• Healthy man and woman between 18-60 years old (inclusive) for the adult cohort and between 61-75 years old (inclusive) for the elderly cohort.

• Have a body-mass index of 18.0-30.0 kg/m² at screening

• Give informed consent prior to study enrollment and all study procedures

• Participants must be able to comply with study procedures and be available for all study visits

• Participants must be in general good health based on medical history and physical examination as determined by the investigator(s) at Screening

• Participants must have haematology, clinical chemistry, coagulation, and urinalysis test results that are not deviating from the normal reference range by age and gender, or considered "not clinicallysignificant" per investigator decision based on safety at Screening.

• Males must be surgically sterile (>30 days since vasectomy with no viable sperm), practice true abstinence, or, if engaged in sexual activities with a female with childbearing potential, use condoms from first vaccination until 60 days after the last vaccination.

• Females of child-bearing potential must practice true abstinence, or, if engaged in sexual activities with a male, agree to use highly effective (failure rate of <1% per year when used consistently and correctly), double-barrier contraceptive measures throughout the study and intend to continue use of contraception methods for at least 60 days following the last vaccination.

• Female participants of child-bearing potential must have negative serum pregnancy test by beta human chorionic gonadotropin [β-HCG] at Screening and a negative urine-based pregnancy test within 24 hours prior to each investigational vaccine administration

• Female participants of childbearing potential must not be pregnant or breastfeeding.

• Women of non-child-bearing potential must:

  1. be classified as being postmenopausal (defined as having a history of amenorrhea for at least one year), or
  2. where history of amenorrhea is less than one year, female participants must have a follicle stimulating hormone (FSH) level > 40 milli-international units per millilitre (mIU/mL), or
  3. have a documented status of being surgically sterile (hysterectomy, bilateral oophorectomy, or /salpingectomy).

• All volunteers will be screened for serum antibodies against SARS-CoV-2, as evidence of previous infection using Enzyme-Linked Immunosorbent Assay (ELISA) and must have a negative result

• Body temperature measured at forehead using validated device must be less than 37.5ºC at Screening.

• Pulse must be no greater than 100 beats per minute, at Screening

• Systolic blood pressure (SBP) must be between 85 to 150 millimeters of mercury (mm Hg), inclusive, at Screening

• Participants must agree to refrain from donating blood, plasma, ovules, sperm, or organs during the whole study

Exclusion Criteria:

• Presence of clinically significant medical history, unstable chronic or acute disease, or physical, or laboratory findings that in the opinion of the PI may potentially increase the expected risk of exposure to the investigational vaccine, compromise the safety of the participant, or interfere with any aspect of study conduct or interpretation of results. This will include any thrombocytopenia or bleeding disorder contraindicating IM vaccination.
• Presence of self-reported or medically documented significant medical or psychiatric condition(s) as judged by the investigator(s) that it may not be in the participant's interest to participate in the study.
• Presence of an acute illness, as determined by the participating Study Site investigator(s), with or without fever (forehead temperature measured by validated device ≥ 37.5 ºC) within 72 hours prior to each vaccination
• Presence of birthmarks, tattoos, wound, or other skin conditions over the deltoid region of both arms that in the opinion of the investigator(s), could reasonably obscure and interfere with evaluation of local ISRs
• Inadequate venous access to allow collection of blood samples
• Breastfeeding or planning to breastfeed from the time of the first vaccination to after the last vaccination, or pregnant as confirmed by a positive serum β-HCG pregnancy test at Screening or positive urine pregnancy test at subsequent clinic visits at timepoints as delineated in the schedule of assessments
• Received any prophylactic or therapeutic vaccine, or licensed or unlicensed vaccine, device, or blood product, within 4 weeks of first vaccination or 5 half-lives (whichever is longer), or anticipate to do so in the follow-up period defined for this study
• History of severe allergy (requiring hospital care), anaphylaxis, severe reaction to any drug or prior vaccination, or any known or suspected allergies or sensitivities to any component of the investigational vaccine or tobacco
• Participant is immunosuppressed as caused by disease (such as HIV)
• Chronic use (more than 14 continuous days) of or anticipated need to use, within the next 6 months, of any medications that may be associated with impaired immune responsiveness or with immunosuppression
• History of hepatitis B or hepatitis C infection
• Receipt of immunoglobulins or blood products within 90 days of the first vaccination
• Requirement for antipyretic or analgesic medication on a daily or every other day basis from enrolment through 72 hours after vaccination
• Current use of any prescription or over-the-counter medications within 7 days prior to vaccination, unless approved by the PI
• Receipt of other investigational products (drug, biologic or device) within 60 days before the first vaccination
• History of alcohol or drug abuse that in the opinion of the PI could affect the participant's safety or compliance with study
• Participant is unwilling to abstain from blood donation during the course of the study, and/or is participating in any research study involving blood sampling (more than 450 mL /unit of blood), or blood donation to any blood bank during the 2 months prior to the Screening visit
• Participant is unwilling to abstain from donating plasma, ovules, sperm, or organs during the course of the study
• Close contact with anyone known to have SARS-CoV-2 infection within 30 days prior to vaccine administration
• History of COVID-19 diagnosis
• Has a positive result on SARS-CoV-2 antibody IgG/IgM measured by ELISA at screening
• On current treatment with investigational agents for prophylaxis of COVID-19 including COVID-19 Vaccine under EUA.
• Planning to travel out of the country from enrolment through 29 days after the second vaccination
• Residing in a nursing home or other skilled nursing facility or having a requirement for skilled nursing care
• Is a participant at high risk of SARS-CoV2 exposure in the opinion of the PI, including but not limited to an occupation (e.g., healthcare workers, active health care workers with direct patient contact, emergency response personnel) or close contact with a SARS-CoV-2 positive confirmed case (e.g. family member, housemate)
• A chronic smoker (defined as ≥10 Pack years [packs/day × years smoked]) within the 12 months prior to enrolment (For Elderly Participants only)