Immunogenicity and Safety Study of SCB-2023 Vaccine as a Booster in Adults

Study Overview
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Brief Summary
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The purpose of this study is to assess the immunogenicity and safety of SCB-2023 trivalent vaccine compared to the prototype SCB-2019 monovalent vaccine in participants previously vaccinated with 3 doses of inactivated COVID-19 vaccine ≥6 months prior to enrollment.

Official Title
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Phase 3, Multi-center, Observer-blind, Randomized, Controlled Study to Evaluate the Immunogenicity and Safety of SCB-2023 Vaccine Administered as a Booster Dose to Adults Who Previously Received COVID-19 Vaccine

Conditions
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COVID-19

Intervention / Treatment
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* Biological: SCB-2023 vaccine (trivalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection
* Biological: SCB-2019 (monovalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Male or female ≥18 years of age. Individuals willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests and other study procedures. Individuals willing and able to give an informed consent, prior to screening. Healthy participants or participants with pre-existing medical conditions who are in a stable medical condition. Individuals who received three doses of inactivated COVID-19 vaccine. Exclusion Criteria: Body temperature >37.8°C (axillary), or any acute illness at baseline. Confirmed SARS-CoV-2 infectionor with known history of COVID-19. Individuals who have received an investigational or licensed COVID-19 vaccine prior to Day 1 (except for inactivated COVID-19 vaccine). Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease or immunosuppressive/cytotoxic therapy. Any progressive unstable or uncontrolled clinical conditions. Individuals who are pregnant, or breastfeeding, or planning to become pregnant while enrolled in this study or during the study period. History of severe adverse reaction associated with a vaccine or severe allergic reaction. History of malignancy within 1 year before screening. Individuals who have received any other investigational product. Individuals who have received any other licensed vaccines within 14 days prior to enrollment. Treatment with Rituximab or any other anti-CD20 monoclonal antibodies. Known bleeding disorder that would, in the opinion of the investigator, contraindicate i.m. injection. Administration of intravenous immunoglobulins and/or any blood products. Any condition that, in the opinion of the investigator, would interfere with the primary study objectives or pose additional risk to the participant.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: SCB-2023 arm<br>Participants will receive one booster dose with SCB-2023 vaccine on Day 1 | Biological: SCB-2023 vaccine (trivalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection<br>* SCB-2023 vaccine (trivalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection<br>|
| Active Comparator: SCB-2019 arm<br>Participants will receive one booster dose with SCB-2019 vaccine on Day 1 | Biological: SCB-2019 (monovalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection<br>* SCB-2019 (monovalent), a recombinant SARS-CoV-2 trimeric S-protein subunit vaccine for COVID-19; intramuscular injection<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To demonstrate that SCB-2023 vaccine elicits an immune response superior to SCB-2019 for Omicron BA.5 | GMT ratio | Day 15 | 
| To demonstrate that SCB-2023 vaccine elicits an immune response superior to SCB-2019 for Omicron XBB.1.5 | GMT ratio | Day 15 | 
| Assess the reactogenicity of SCB-2023 vaccine compared to SCB-2019 vaccine | Proportion of participants with local and systemic AEs | Day 7 | 
| Assess the safety of SCB-2023 vaccine compared to SCB-2019 vaccine | Proportion of participants with unsolicited AEs | Day 29 | 
| Assess the safety of SCB-2023 vaccine compared to SCB-2019 vaccine | Proportion of participants with SAE, AEs leading to early termination from study, MAAEs, and AESIs | Up to 1 year post-vaccination | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Non-inferiority with respect to ratio of the geometric mean of Omicron BA.5 titer in SCB-2023 recipients and SARS-CoV-2 Delta titers in SCB-2019 recipients, as measured by virus neutralization assay. | GMT ratio | Day 15 | 
| Geometric mean titers elicited by SCB-2023 vaccine and SCB-2019 vaccine by virus neutralization assay against Omicron BA.5 and Omicron XBB1.5. | GMTs; GMFRs; SCRs; Proportion of participants with antibody titer ≥ LLoQ | Day 1, 15, 180 | 
| Geometric mean fold rise elicited by SCB-2023 vaccine and SCB-2019 vaccines by virus neutralization assay against Omicron BA.5 and Omicron XBB1.5 | GMFRs | Day 1, 15, 180 | 
| Proportion of subjects with seroconversion by virus neutralization assay against Omicron BA.5 and Omicron XBB1.5 | SCRs | Day 1, 15, 180 | 
| Proportion of subjects with antibody titer >=LLOQ by virus neutralization assay against Omicron BA.5 and Omicron XBB1.5 | Proportion of participants with antibody titer ≥ LLoQ | Day 1, 15, 180 | 
| Geometric mean titers elicited by SCB-2023 vaccine and SCB-2019 vaccine by virus neutralization assay against SARS-CoV-2 variants of concern | GMTs | Day 1, 15 | 
| Geometric mean fold rise elicited by SCB-2023 vaccine and SCB-2019 vaccines by virus neutralization assay against SARS-CoV-2 variants of concern | GMFRs | Day 1, 15 | 
| Proportion of subjects with seroconversion by virus neutralization assay against SARS-CoV-2 variants of concern | SCRs | Day 1, 15 | 
| Proportion of subjects with antibody titer >=LLOQ by virus neutralization assay against SARS-CoV-2 variants of concern | Proportion of participants with antibody titer ≥ LLoQ | Day 1, 15 |