Phase 3 N=9,902 Randomized Triple-blind Prevention

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

SARS-CoV-2

Bottom Line

View on ClinicalTrials.gov: NCT05212948 ↗

Enrolled (actual)

9,902

Serious AEs

1.7%

Results posted

Nov 2025

Primary outcome: Primary: 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 — 323; 239 Participants — p=0.2409

Study Design & Population

Study type: Interventional
Phase: Phase 3
Interventions: S-268019-b (Drug); Placebo (Drug)
Age: Adult, Older Adult · 18+ yrs
Sex: All
Sponsor: Shionogi
Primary completion: Dec 2022

Outcome Measures

Outcome	Result	p-value
PRIMARY 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	323; 239	0.2409
SECONDARY 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	0; 1	—
SECONDARY Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Symptomatic COVID-19 in the Initial Vaccination Period	457; 313	—
SECONDARY Number of Participants With First Occurrence of SARS-CoV-2 RT-PCR-Positive Severe COVID-19 in the Initial Vaccination Period	0; 1	—
SECONDARY 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	331; 242	—
SECONDARY 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	0; 1	—
SECONDARY 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	479; 324	—
SECONDARY 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	0; 1	—
SECONDARY Number of Participants With First Occurrence of Asymptomatic SARS-CoV-2 Infection in the Initial Vaccination Period	2543; 1345	—
SECONDARY Percentage of Participants Experiencing Solicited Systemic Adverse Events	32.7; 23.4	—
SECONDARY Percentage of Participants Experiencing Solicited Local Adverse Events	37.7; 14.6	—
SECONDARY Geometric Mean Titer (GMT) of SARS-CoV-2 Neutralizing Antibody	34.66; 2.69	—
SECONDARY Geometric Mean Fold Rise (GMFR) of SARS-CoV-2 Neutralizing Antibody	13.86; 1.08	—
SECONDARY Seroconversion Rate of SARS-CoV-2 Neutralizing Antibody	93.1; 3.6	—
SECONDARY GMT of Anti-SARS-CoV-2 S-protein Immunoglobulin G (IgG) Antibody	25209.25; 6.39	—
SECONDARY GMFR of Anti-SARS-CoV-2 S-protein IgG Antibody	6710.95; 1.46	—
SECONDARY Seroconversion Rate of Anti-SARS-CoV-2 S-protein IgG Antibody	98.2; 7.1	—

Summary

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.

Eligibility Criteria

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.

View full record on ClinicalTrials.gov →

Data sourced from ClinicalTrials.gov (NCT05212948). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication.