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

November 14, 2025 updated by: Shionogi

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

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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).

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
9902

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Vietnam
    • Dak Lak
      • Buon Ma Thuot, Dak Lak, Vietnam
        • Buon Ma Thuot City Medical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: S-268019-b, Then Placebo
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
Solution for IM injection
Drug: Placebo
Saline solution for IM injection
Experimental: Placebo, Then S-268019-b
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
Solution for IM injection
Drug: Placebo
Saline solution for IM injection

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Number of Participants With First Occurrence of SARS-CoV-2 Reverse Transcription Polymerase Chain Reaction (RT-PCR)-Positive Symptomatic COVID-19 With Onset at Least 14 Days Following Second Vaccination During the Initial Vaccination Period
Time Frame: From Day 43 (14 days after the second dose administration) to Day 224
Participants without evidence of infection before vaccination (that is, seronegative and PCR-negative at baseline) were determined to have symptomatic COVID-19 when at least 1 protocol-specified COVID-19-related symptom and a positive RT-PCR test result were confirmed by the medical monitor within at least 14 days following the second vaccination. RT-PCR testing was based upon nasopharyngeal swab sampling at protocol-specified timepoints.
From Day 43 (14 days after the second dose administration) to Day 224

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
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
Time Frame: From Day 43 (14 days after the second dose administration) to Day 224
For participants without evidence of infection before vaccination (that is, seronegative and PCR-negative at baseline) who were confirmed to have symptomatic COVID-19 within at least 14 days following the second vaccination, the investigator evaluated if the maximum intensity during the course of the disease met protocol-specified criteria for severe COVID-19.
From Day 43 (14 days after the second dose administration) to Day 224
Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Symptomatic COVID-19 in the Initial Vaccination Period
Time Frame: Up to Day 224
Participants without evidence of infection before vaccination (that is, seronegative and PCR-negative at baseline) were determined to have symptomatic COVID-19 when at least 1 protocol-specified COVID-19-related symptom and a positive RT-PCR test result were confirmed by the medical monitor. RT-PCR testing was based upon nasopharyngeal swab sampling at protocol-specified timepoints.
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
Time Frame: Up to Day 224
For participants without evidence of infection before vaccination (that is, seronegative and PCR-negative at baseline) who were confirmed to have symptomatic COVID-19, the investigator evaluated if the maximum intensity during the course of the disease met the protocol-specified criteria for severe COVID-19.
Up to Day 224
Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Symptomatic COVID-19 in the Initial Vaccination Period Regardless of Serostatus or PCR Status at Baseline With Onset at Least 14 Days Following Second Vaccination
Time Frame: From Day 43 (14 days after the second dose administration) to Day 224
A participant was determined to have symptomatic COVID-19 when at least 1 protocol-specified COVID-19-related symptom and a positive RT-PCR test result were confirmed by the medical monitor within at least 14 days following the second vaccination. RT-PCR testing was based upon nasopharyngeal swab sampling at protocol-specified timepoints.
From Day 43 (14 days after the second dose administration) to Day 224
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 Regardless of Serostatus or PCR Status at Baseline
Time Frame: From Day 43 (14 days after the second dose administration) to Day 224
For participants confirmed to have symptomatic COVID-19 within at least 14 days following the second vaccination, the investigator evaluated if the maximum intensity during the course of the disease met the protocol-specified criteria for severe COVID-19.
From Day 43 (14 days after the second dose administration) to Day 224
Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Symptomatic COVID-19 in the Initial Vaccination Period Regardless of Serostatus or PCR Status at Baseline
Time Frame: Up to Day 224
A participant was determined to have symptomatic COVID-19 when the participant had at least 1 protocol-specified COVID-19-related symptom and a positive RT-PCR test result confirmed by the medical monitor. RT-PCR testing was based upon nasopharyngeal swab sampling at protocol-specified timepoints.
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 Regardless of Serostatus or PCR Status at Baseline
Time Frame: Up to Day 224
For participants confirmed to have symptomatic COVID-19, the investigator evaluated if the maximum intensity during the course of the disease met the protocol-specified criteria for severe COVID-19.
Up to Day 224
Number of Participants With First Occurrence of Asymptomatic SARS-CoV-2 Infection in the Initial Vaccination Period
Time Frame: From Day 43 (14 days after the second dose administration) to Day 224
For participants without evidence of infection before vaccination (that is, seronegative and PCR-negative at baseline), asymptomatic SARS-CoV-2 infection was defined as having a positive result of anti-SARS-CoV-2 N-protein antibody test beginning 14 days following the second vaccination and not meeting the protocol-specified criteria of symptomatic COVID-19. Antibodies to SARS-CoV-2 N-protein were used to determine both natural infection and the incidence of asymptomatic infection acquired during the initial vaccination period of the study.
From Day 43 (14 days after the second dose administration) to Day 224
Percentage of Participants Experiencing Solicited Systemic Adverse Events
Time Frame: Up to Day 224
An adverse event (AE) was defined as any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. Solicited systemic AEs were defined as the AEs that occurred within the first 7 days after each vaccination and were classified as one of the following: fever, nausea/vomiting, diarrhea, headache, fatigue, and myalgia. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.
Up to Day 224
Percentage of Participants Experiencing Solicited Local Adverse Events
Time Frame: Up to Day 224
An AE was defined as any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. Solicited local AEs were defined as the AEs that occurred within the first 7 days after each vaccination and were classified as one of the following: pain, erythema/redness, induration, and swelling. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.
Up to Day 224
Geometric Mean Titer (GMT) of SARS-CoV-2 Neutralizing Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The serum neutralizing antibody level against SARS-CoV-2 was measured by a live virus neutralization assay. The GMT was calculated by taking the back transformation of the arithmetic mean of log-transformed titers. The 95% confidence interval was calculated based on the Student's t distribution of the log-transformed values, then back transformed to the original scale.
Day 57
Geometric Mean Fold Rise (GMFR) of SARS-CoV-2 Neutralizing Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The serum neutralizing antibody level against SARS-CoV-2 was measured by a live virus neutralization assay. The GMFR was calculated by taking the back transformation of the arithmetic mean of the change from baseline in log-transformed titers. The 95% confidence interval was calculated based on the Student's t distribution of the change from baseline in the log-transformed values, then back transformed to the original scale.
Day 57
Seroconversion Rate of SARS-CoV-2 Neutralizing Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The serum neutralizing antibody level against SARS-CoV-2 was measured by a live virus neutralization assay. Seroconversion was defined as a 4-times or higher from baseline in SARS-CoV-2 neutralizing antibody titer, where titer values reported as below the lower limit of quantification (LLOQ) were replaced by 0.5*LLOQ. Seroconversion rate was defined as the percentage of participants that underwent seroconversion. The 95% confidence interval was calculated using the Clopper-Pearson method.
Day 57
GMT of Anti-SARS-CoV-2 S-protein Immunoglobulin G (IgG) Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The serum neutralizing antibody level against SARS-CoV-2 (anti-spike protein IgG antibody) was measured by a chemiluminescence immunoassay. The GMT was calculated by taking the back transformation of the arithmetic mean of log- transformed titers. The 95% confidence interval was calculated based on the Student's t distribution of the log-transformed values, then back transformed to the original scale.
Day 57
GMFR of Anti-SARS-CoV-2 S-protein IgG Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The anti-spike protein IgG antibody was measured by a chemiluminescence immunoassay. The GMFR was calculated by taking the back transformation of the arithmetic mean of the change from baseline in log-transformed titers. The 95% confidence interval was calculated based on the Student's t distribution of the change from baseline in the log-transformed values, then back transformed to the original scale.
Day 57
Seroconversion Rate of Anti-SARS-CoV-2 S-protein IgG Antibody
Time Frame: Day 57
Blood samples for immunogenicity assessments were collected during protocol-specified study visits. The anti-spike protein IgG antibody was measured by a chemiluminescence immunoassay. Seroconversion was defined as a 4-times or higher from baseline in anti-spike protein IgG antibody titer, where titer values reported as below the LLOQ are replaced by 0.5*LLOQ and titer values reported as above the upper limit of quantification (ULOQ) are imputed at the ULOQ value. Seroconversion rate was defined as the percentage of participants that underwent seroconversion. The 95% confidence interval was calculated using the Clopper-Pearson method.
Day 57

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Shionogi

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 25, 2021

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 19, 2022

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 19, 2023

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
January 24, 2022

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 24, 2022

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
January 28, 2022

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 28, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 14, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 2126U0232

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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