A Study of S-268019 for the Prevention of COVID-19

Study Overview
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Brief Summary
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The main purpose of this study is to assess the efficacy of S-268019-b for the prevention of COVID-19 in the initial vaccination period prior to crossover in participants without evidence of infection before vaccination as compared to placebo.

Detailed Description
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Eligible participants will be randomized to receive either S-268019-b or placebo first and then will be crossed over to receive the opposite intervention. The study will consist of two treatment periods, an initial vaccination period (Day 1 to Day 224), and a crossover vaccination period (Day 225 to Day 435).

Official Title
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A Phase 3, Randomized, Observer-Blind, Placebo- Controlled Cross-over Study to Evaluate the Efficacy, Safety, and Immunogenicity of S-268019 for the Prevention of COVID-19

Conditions
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SARS-CoV-2

Intervention / Treatment
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* Drug: S-268019-b
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Agree not to participate in any other SARS-CoV-2 prevention trial during the study follow-up. Capable of using Diary without difficulties (if applicable, with assistance by caregiver). Exclusion Criteria: Current or history of a laboratory-confirmed diagnosis of SARS-CoV-2 infection or COVID-19. Unstable current cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, or neurological disease that, in the opinion of the investigator or subinvestigator, would constitute a safety concern or confound data interpretation. Immunosuppression (immunodeficiency, acquired immunodeficiency syndrome [AIDS], use of systemic steroids, use of immunosuppressants within the past 6 months prior to the first dose of study intervention, treatment for malignant tumors, other immunosuppressive therapy). Previous vaccination against SARS-CoV-2. Any inactivated vaccine received within 14 days prior to the first dose of study intervention. Any live vaccine received within 28 days prior to the first dose of study intervention. Immunoglobulin preparations, blood products, or a blood transfusion within 3 months prior to the first dose of study intervention. Other inclusion and exclusion criteria may apply.

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: Crossover Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: S-268019-b, Then Placebo<br>Participants will first receive a dose of S-268019-b via intramuscular (IM) injection on Day 1 and Day 29 during the initial vaccination period. After the initial vaccination period, participants will then receive a placebo IM injection (matching S-268019-b) on Day 225 and Day 253. | Drug: S-268019-b<br>* Solution for IM injection<br>Drug: Placebo<br>* Saline solution for IM injection<br>|
| Experimental: Placebo, Then S-268019-b<br>Participants will first receive a dose of placebo IM injection (matching S-268019-b) on Day 1 and Day 29 during the initial vaccination period. After the initial vaccination period, participants will then receive S-268019-b IM injection on Day 225 and Day 253. | Drug: S-268019-b<br>* Solution for IM injection<br>Drug: Placebo<br>* Saline solution for IM injection<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Participants With First Occurrence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Reverse Transcription Polymerase Chain Reaction (RT-PCR)-Positive Symptomatic COVID-19 in the Initial Vaccination Period |  | 14 days after the second dose administration | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Severe COVID-19 in the Initial Vaccination Period with Onset at Least 14 Days Following Second Vaccination |  | 14 days after the second dose administration | 
| Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Symptomatic COVID-19 in the Initial Vaccination Period |  | Up to Day 224 | 
| Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Severe COVID-19 in the Initial Vaccination Period |  | Up to Day 224 |