This phase 1/2 study will evaluate the safety, reactogenicity and immunogenicity of SCB-1022 and SCB-1033 compared to SCB-1019T (Parts 1 and 2) or Placebo (Part 3).

In Part 1 and Part 2, the study will descriptively evaluate three dose levels of SCB-1022 and SCB-1033. Part 3 will descriptively compare SCB-1022 and SCB-1033 against placebo.

The sample size of this study is not based on formal statistical hypothesis testing but is acceptable for safety and immunogenicity evaluation in a phase 1/2 study. The study will be overseen by a safety monitoring committee.

Inclusion Criteria:

• Male and female participants 60 to 85 years of age at the screening visit.
• Individuals willing and able to comply with study requirements, including all scheduled visits, vaccination, laboratory tests, and other study procedures.
• Individuals willing and able to give an informed consent, prior to screening.
• Healthy participants as determined by medical history, physical examination, and clinical judgment of the investigator; participants with pre-existing stable medical conditions can be included.

Please refer to Protocol for full list of Inclusion and Exclusion criteria.

Exclusion Criteria:

• Pregnancy or potential to become pregnant during the study.
• Acute disease or fever (≥38°C) at time of vaccination.
• History of Guillain-Barré Syndrome (GBS).
• Recurrent or un-controlled neurological disorders or seizures.
• Serious or unstable chronic illnesses. Please refer to Protocol for full list of Inclusion and Exclusion criteria.