A Double-blind, Randomized, Controlled, Phase 2/3 Study to Evaluate the Efficacy, Immunogenicity, and Safety of CpG 1018/Alum-Adjuvanted Recombinant SARS-CoV-2 Trimeric S-protein Subunit Vaccine (SCB-2019) for the Prevention of SARS-CoV-2- Mediated COVID-19 in Participants Aged 12 Years and Older

• Male or females ≥12 years of age, inclusive\*.

• 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.

• Healthy adult or adolescent subjects or adult or adolescent subjects 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

• Female subjects who are WOCBP are eligible to participate in the study if not pregnant, not breastfeeding, and at least 1 of the following criteria apply:

‣ 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.

• 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.

• Individuals (or their legally acceptable representative based on local regulations) willing and able to give an informed consent, prior to screening. For adolescent subjects: informed assent signed by adolescents and informed consent signed by the parent(s) or legally acceptable representative(s) as per local requirements.

• Applicable for HIV-positive individuals only if:

∙ They are medically stable at screening, as determined by the investigator, and free of opportunistic infections in the 1 year prior to first study vaccination, and They have an HIV-1 viral load \<1000 copies/mL within 45 days of randomization in the study, and They are receiving highly active antiretroviral therapy (HAART) for at least 3 months before screening. Changes in antiretroviral dosage within 3 months of entering the study are allowed, as are exchanges in pharmacological formulations.