1. Male or females ≥18 years of age, inclusive. 2. Participants who are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests, the electronic completion of the COVID-19 ePRO and other study procedures. 3. Healthy adults or adults with pre-existing medical conditions who are in stable condition. A stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months before enrollment. Note: The first 200 individuals enrolled in the Phase 2 part of the study should be healthy subjects 18 to 64 years or age without comorbidities associated with a high risk of severe COVID-19. 4. Female subjects are eligible to participate in the study if not pregnant, not breastfeeding, and at least 1 of the following criteria apply: Women of childbearing potential (WOCBP) must have a negative urine pregnancy test prior to each vaccination. A confirmatory serum pregnancy test may be conducted at the Investigator’s discretion. They must be using a highly effective licensed method of birth control for 30 days prior to the first vaccination and must agree to continue such precautions during the study until 90 days after the second vaccination. 5. Male subjects must agree to employ acceptable contraception from the day of first dose of the study vaccine/placebo until 6 months after the last dose of the study vaccine/placebo and also refrain from donating sperm during this period. 6. Individuals (or their legally acceptable representative based on local regulations) willing and able to give an informed consent, prior to screening.

1. Male or females ≥18 years of age, inclusive. 2. Participants who are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests, the electronic completion of the COVID-19 ePRO and other study procedures. 3. Healthy adults or adults with pre-existing medical conditions who are in stable condition. A stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months before enrollment. Note: The first 200 individuals enrolled in the Phase 2 part of the study should be healthy subjects 18 to 64 years or age without comorbidities associated with a high risk of severe COVID-19. 4. Female subjects are eligible to participate in the study if not pregnant, not breastfeeding, and at least 1 of the following criteria apply: Women of childbearing potential (WOCBP) must have a negative urine pregnancy test prior to each vaccination. A confirmatory serum pregnancy test may be conducted at the Investigator’s discretion. They must be using a highly effective licensed method of birth control for 30 days prior to the first vaccination and must agree to continue such precautions during the study until 90 days after the second vaccination. 5. Male subjects must agree to employ acceptable contraception from the day of first dose of the study vaccine/placebo until 6 months after the last dose of the study vaccine/placebo and also refrain from donating sperm during this period. 6. Individuals (or their legally acceptable representative based on local regulations) willing and able to give an informed consent, prior to screening.