CLO-SCB-1019-002 is the first study of SCB-1019T vaccine for revaccination in older adults who were previously vaccinated with AREXVY. The safety, tolerability and immunogenicity of SCB-1019T are assessed.

The study design will compare heterologous revaccination with SCB-1019T, homologous revaccination with AREXVY, or placebo in adults who were previously vaccinated with AREXVY. The sample size for this study is not based on formal statistical hypothesis testing but is acceptable for safety and immunogenicity evaluation in a phase 1 study. The study will be overseen by a safety monitoring committee.

Inclusion Criteria:

1. Male and female participants 60-85 years of age at the screening visit and who received AREXVY before.
2. Individuals are willing and able to comply with study requirements, including all scheduled visits, vaccination, laboratory tests, and other study procedures.
3. Individuals willing and able to give an informed consent, prior to screening.
4. 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 (a stable medical condition is defined as a disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months before enrollment).

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

Exclusion Criteria:

1. Acute disease or fever (≥38°C) at time of vaccination. Participants with a minor illness (mild diarrhea, mild upper respiratory infection) without fever may be enrolled at the discretion of the investigator. For participants with minor illness and/or fever at the time of vaccination, Visit 1 may be rescheduled within the allowed time-window.
2. Recurrent or un-controlled neurological disorders or seizures.
3. Serious or unstable chronic illnesses
4. Any history of dementia or any medical condition that moderately or severely impairs cognition
5. History of a severe adverse reaction associated with a vaccine or severe allergic reaction (e.g., anaphylaxis) to any component of the study vaccines.

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