First-in-human Safety and Immunogenicity Study of SCB-1019 in Healthy Adults

This phase 1 study in Australia will evaluate the safety, reactogenicity and immunogenicity of the bivalent SCB-1019 vaccine candidate with or without aluminium hydroxide in young adults (18-59 years) and older adults (60-85 years).

The study design includes an age- and dose-escalation (low/high dose) in two adult age groups (young adults \[18-59 years\] and older adults \[60-85 years\]). Study will be conducted in two parts, part 1 will enrolled young adults and part 2 will enroll older adults. A sentinel dosing approach will be used for close monitoring of safety to minimize risk to participants. Detailed characterization of safety (including safety laboratory evaluation) and immune responses is planned. A placebo will be used as a control. 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.

Eligibility Criteria:
Inclusion Criteria:

* Male and female participants 18 to 59 years of age (Part 1) and 60 to 85 years of age (Part 2) 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 (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).
* Female of childbearing potential willing to use a highly effective contraceptive method from 30 days before until 90 days after vaccination and have a negative pregnancy test on the day of vaccination; males able to father children and willing to use a highly effective contractive method from vaccination up to 90 days after vaccination, and agree to refrain from donating sperm during this period.

Exclusion Criteria:

* 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.
* History of a severe adverse reaction associated with a vaccine or severe allergic reaction (e.g., anaphylaxis) to any component of the study vaccines.
* Previous vaccination with an RSV vaccine at any time before vaccination (Day 1), or planned receipt during the study of a non-study RSV vaccine.
* Receipt of any other licensed vaccines within 14 days before vaccination (Day 1) or planned receipt of any vaccine up to 28 days after study vaccination (Day 29).
* Receipt of any other investigational product within 30 days before vaccination (Day 1) or intention to participate in another clinical study at any time during the conduct of this study.
* Any condition that, in the opinion of the investigator, would interfere with the primary study objectives or pose additional risk to the participant.
* Receipt of intravenous immunoglobulins and/or any blood products within 60 days before vaccination (Day 1) or planned administration during the study period.
* Individuals with positive test result for hepatitis B surface antigen, hepatitis C virus antibody, and/or human immunodeficiency virus types 1 or 2 antibodies at screening.
* Immunocompromised with known or suspected immunodeficiency, as determined by medical history and/or laboratory/physical examination (no laboratory testing required).
* Receipt of any immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, e.g. for cancer, organ transplantation or autoimmune disease, within three months prior to vaccination or planned receipt during the study. If a short-term course of systemic corticosteroids (\<14 days) has been administered for treatment of an acute illness, participants should not be enrolled into the study until corticosteroid therapy has been discontinued for at least 28 days before study vaccination. Inhaled/nebulized, intraarticular, intrabursal, or topical (skin or eye) corticosteroids are permitted.
* Treatment with rituximab or any other anti-CD20 monoclonal antibodies within nine months prior to vaccination or planned during the study period.
* History of malignancy within one year before vaccination (exceptions are squamous and basal cell carcinomas of the skin and carcinoma in situ of the cervix which has been cured, or other malignancies with minimal risk of recurrence).
* Any screening safety laboratory values (hematology, biochemistry, coagulation, and urinalysis) that meet the definition of a ≥Grade 1 abnormality (according to the toxicity grading)