Study to Assess Safety and Immunogenicity of an Egg-based H5N8 Influenza Vaccine at Multiple Dose Levels Adjuvanted With Matrix-M in Healthy Participants 18 Years of Age and Above.

September 11, 2026 updated by: Sanofi

A Phase 1/2, Parallel, Observer-blind Study to Assess the Safety and Immunogenicity of an Egg-based H5N8 Influenza Vaccine at Multiple Dose Levels Adjuvanted With Matrix-M in Healthy Participants 18 Years of Age and Above.

The study aims to evaluate an egg-based H5N8 influenza vaccine up to 3 dose levels (low, medium, and high dose) given with or without adjuvant to see if the adjuvant improves vaccine effectiveness.

The study will enroll healthy adults aged 18 years and over. Participants will receive 2 injections in their arm of either one of the 3 dose levels of the study vaccine (low, medium, or high dose) with the adjuvant or the unadjuvanted vaccine (high dose).

Study duration per participant: approximately 14 months (including screening visit).

Study Overview

Status

Status

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

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.

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 (Estimated)

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.
640

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 2
  • Phase 1

Contacts and Locations

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

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.
  • Name: Trial Transparency email recommended (Toll free for US & Canada)
  • Phone Number: option 6 800-633-1610
  • Email: contact-us@sanofi.com

Study Locations

  • United States
    • Arizona
      • Tempe, Arizona, United States, 85281
        • Recruiting
        • AMR Clinical Phoenix, Arizona- Site Number : 8400004
    • California
      • Rolling Hills Estates, California, United States, 90274
        • Recruiting
        • Peninsula Research Associates- Site Number : 8400011
      • San Diego, California, United States, 92123
        • Recruiting
        • California Research Foundation- Site Number : 8400007
    • Florida
      • Coral Gables, Florida, United States, 33134
        • Recruiting
        • Alliance for Multispeciality Research - Coral Gables- Site Number : 8400003
      • DeLand, Florida, United States, 32720
        • Recruiting
        • Accel Research Sites Network - DeLand Clinical Research Unit- Site Number : 8400017
      • Fort Myers, Florida, United States, 33912
        • Recruiting
        • Alliance for Multispeciality Research - Fort Myers- Site Number : 8400001
      • Miami Lakes, Florida, United States, 33016
        • Recruiting
        • Indago Research & Health Center- Site Number : 8400010
    • Georgia
      • Decatur, Georgia, United States, 30030
        • Recruiting
        • Accel Research Sites - NeuroStudies- Site Number : 8400014
      • Decatur, Georgia, United States, 30030
        • Recruiting
        • iResearch Atlanta- Site Number : 8400008
    • Illinois
      • Oak Brook, Illinois, United States, 60523
        • Recruiting
        • AMR Chicago- Site Number : 8400005
    • Kansas
      • Newton, Kansas, United States, 67114
        • Recruiting
        • AMR Clinical Newton, Kansas- Site Number : 8400006
    • New York
      • Rochester, New York, United States, 14609
        • Recruiting
        • Rochester Clinical Research- Site Number : 8400012
    • South Carolina
      • North Charleston, South Carolina, United States, 29405
        • Recruiting
        • Coastal Carolina Research Center - North Charleston- Site Number : 8400018
    • Tennessee
      • Knoxville, Tennessee, United States, 37909
        • Recruiting
        • Alliance for Multispecialty Research - Weisgarber Medical Park- Site Number : 8400002
    • Utah
      • Salt Lake City, Utah, United States, 84107
        • Recruiting
        • CenExel JRB - Salth Lake City- Site Number : 8400009
    • Virginia
      • Charlottesville, Virginia, United States, 22911
        • Recruiting
        • Charlottesville Medical Research- Site Number : 8400016

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

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Aged 18 years or above on the day of inclusion
  • Participants who are healthy as determined by medical evaluation including medical history
  • Not pregnant/breastfeeding; non-childbearing potential or uses effective contraception/abstinence from ≥4 weeks before the first study intervention dose to ≥8 weeks after the last dose
  • Informed consent form has been signed and dated
  • Able to attend all scheduled visits and to comply with all study procedures
  • Covered by health insurance, if required by local regulations

Exclusion Criteria:

  • Known or suspected immunodeficiency; immunosuppressive therapy in past 6 months; or long-term systemic corticosteroid (eg, prednisone for more than 2 weeks in the past 3 months)
  • Known hepatitis B or hepatitis C infection (based on medical history)
  • Known personal or family history of previous episodes of Guillan-Barré syndrome (GBS), neuritis (including Bell's palsy), convulsions, encephalitis, transverse myelitis, and vasculitis
  • Known systemic hypersensitivity to any of the study intervention components or history of life-threatening reaction to the study interventions or products with same substances
  • Self-reported thrombocytopenia contraindicating intramuscular (IM) injection based on investigator's judgment
  • Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating IM injection based on investigator's judgment
  • Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion
  • History of A/H5 infection prior to the study participation
  • Moderate or severe acute illness/infection (per investigator judgment)/fever (≥ 38.0°C [≥ 100.4°F]) on study intervention day. Include participant only after the condition or fever has resolved
  • Alcohol, prescription drug, or substance abuse that, in the opinion of the investigator, might interfere with the study conduct or completion
  • Any vaccine given 4 weeks before first study intervention or any planned vaccination to be given prior to Day 43 (ie, approximately 21 days after the second study intervention)
  • Previous vaccination against A(H5) with an investigational or marketed vaccine. This includes, but is not limited to, influenza subtypes A(H5N1), A(H5N8), and A(H5N6)
  • Has received a blood transfusion or blood-derived products, including immunoglobulins in the past 3 months
  • Participation in another clinical study for a vaccine, drug, medical device, or medical procedure within 4 weeks before enrollment or planned participation during the present study period
  • Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily
  • Is an investigator, investigator/study center employee, or immediate family member (parent, spouse, natural/adopted child) of the investigator/employee with direct involvement in the study
  • Any screening safety laboratory parameters out of normal ranges and assessed as > Grade 2

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

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: Parallel Assignment
  • Masking: Double

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: Group 1: Flu H5 egg pandemic low dose vaccine, with adjuvant
Participants receive 2 intramuscular injections of flu H5 egg pandemic low dose vaccine, with adjuvant
Biological: Flu H5 egg pandemic low dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Experimental: Group 2: Flu H5 Egg Pandemic medium dose vaccine, with adjuvant
Participants receive 2 intramuscular injections of flu H5 egg pandemic medium dose vaccine, with adjuvant
Biological: Flu H5 Egg Pandemic medium dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Experimental: Group 3: Flu H5 Egg Pandemic high dose vaccine, with adjuvant
Participants receive 2 intramuscular injections of flu H5 egg pandemic high dose vaccine, with adjuvant
Biological: Flu H5 Egg Pandemic high dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Experimental: Group 4: Flu H5 Egg Pandemic high dose vaccine, without adjuvant
Participants receive 2 intramuscular injections of flu H5 egg pandemic high dose vaccine, without adjuvant
Biological: Flu H5 Egg Pandemic high dose vaccine, without adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)

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 immediate Adverse Events (AEs)
Time Frame: Within 30 minutes after each vaccination
Immediate adverse events are medically relevant unsolicited systemic adverse events reported in the 30 minutes after vaccination
Within 30 minutes after each vaccination
Number of participants experiencing solicited administration site reactions (pre-listed in the participant diary and case report form [CRF])
Time Frame: Within 8 days of each vaccination, including the day of vaccination
A solicited reaction is an adverse reaction (sign or symptom) observed and reported under the conditions pre-listed (for example: injection site pain or headache). Solicited administration site reactions are reactions at and around the injection/administration site
Within 8 days of each vaccination, including the day of vaccination
Number of participants experiencing solicited systemic reactions (pre-listed in the participant diary and CRF)
Time Frame: Within 8 days of each vaccination, including the day of vaccination
All solicited reactions that are not solicited injection or administration site reactions
Within 8 days of each vaccination, including the day of vaccination
Number of participants experiencing unsolicited AEs
Time Frame: Within 21 days after the first vaccination, including the day of the first vaccination, and within 28 days after the second vaccination, including the day of the second vaccination
Unsolicited AE: an observed AE that does not fulfill the conditions of solicited reactions
Within 21 days after the first vaccination, including the day of the first vaccination, and within 28 days after the second vaccination, including the day of the second vaccination
Number of participants experiencing Medically Attended Adverse Events (MAAEs)
Time Frame: From Day 01 until the end of the study, approximately 14 months
MAAEs are collected throughout the study
From Day 01 until the end of the study, approximately 14 months
Number of participants experiencing Adverse Events of Special Interest (AESIs)
Time Frame: From Day 01 until the end of the study, approximately 14 months
AESIs are collected throughout the study
From Day 01 until the end of the study, approximately 14 months
Number of participants experiencing Serious Adverse Events (SAEs)
Time Frame: From Day 01 until the end of the study, approximately 14 months
SAEs are collected throughout the study
From Day 01 until the end of the study, approximately 14 months
Number of participants experiencing out-of-range biological test results (including shift from baseline values)
Time Frame: Up to 8 days after each vaccination
Safety laboratory assessments will include clinical chemistry and hematology
Up to 8 days after each vaccination
Number of participants experiencing AEs leading to discontinuation
Time Frame: From Day 01 until the end of the study, approximately 14 months
AEs leading to discontinuation are collected throughout the study
From Day 01 until the end of the study, approximately 14 months
Geometric mean titer of hemagglutination inhibition (HAI) assay antibody (Ab) titer
Time Frame: Day 01 and Day 43
Influenza vaccine antibody titers are measured by HAI assay
Day 01 and Day 43
Number of participants with HAI Ab titer ≥ 40 (1 dilution [dil]; ie, seroprotection)
Time Frame: Day 43
Influenza vaccine antibody titers are measured by HAI assay
Day 43
Number of participants with seroconversion
Time Frame: Day 01 and Day 43
Seroconversion is defined as HAI Ab titer < 10 (1/dil) on Day 01 and post-injection titer ≥ 40 (1/dil) on Day 43; or defined as HAI Ab titer ≥ 10 (1/dil) on Day 01 and a ≥ 4-fold increase in titer (1/dil) on Day 43
Day 01 and Day 43
Geometric mean titer ratio of individual HAI Ab titer ratio Day 43/Day 01
Time Frame: Day 01 and Day 43
Influenza vaccine antibody titers are measured by HAI assay
Day 01 and Day 43

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
Geometric mean titer of hemagglutination inhibition (HAI) assay antibody (Ab) titer obtained on Day 01, Day 22, Day 43, Day 202
Time Frame: Day 01, Day 22, Day 43, Day 202
Influenza vaccine antibody titers are measured by HAI assay
Day 01, Day 22, Day 43, Day 202
Geometric mean titer ratio of individual HAI Ab titer ratios Day 22/Day 01, Day 43/Day 01, Day 202/Day 43
Time Frame: Day 01, Day 22, Day 43, Day 202
Individual HAI Ab titer ratios are calculated for the following time points: Day 22/Day 01, Day 43/Day 01 and Day 202/Day 43
Day 01, Day 22, Day 43, Day 202
Number of participants with individual HAI Ab titer ≥ 40 (1/dil) on Day 01, Day 22, Day 43, Day 202
Time Frame: Day 01, Day 22, Day 43, Day 202
Influenza vaccine antibody titers are measured by HAI assay
Day 01, Day 22, Day 43, Day 202
Number of participants with seroconversion on Day 22 compared to Day 01 (baseline)
Time Frame: Day 01, Day 22
Seroconversion is defined as titer < 10 (1/dil) on Day 01 and post-injection titer ≥ 40 (1/dil) on Day 22; or defined as titer ≥ 10 (1/dil) on Day 01 and a ≥ 4 fold increase in titer (1/dil) on Day 22
Day 01, Day 22
Number of participants with detectable HAI Ab titer
Time Frame: Day 01, Day 22, Day 43, Day 202
Detectable HAI Ab titer: a titer ≥ 10 (1/dil)
Day 01, Day 22, Day 43, Day 202
Geometric mean titer of neutralization (NT) Ab titer
Time Frame: Day 01, Day 22, Day 43, Day 202
Influenza vaccine antibody titers are measured by serum neutralization (SN) assay
Day 01, Day 22, Day 43, Day 202
Geometric mean titer ratio of individual NT Ab titer ratio
Time Frame: Day 01, Day 22, Day 43, Day 202
Individual NT Ab titer ratios are calculated for the following time points: Day 22/Day 01, Day 43/Day 01 and Day 202/Day 43
Day 01, Day 22, Day 43, Day 202
Number of participants with NT Ab titer ≥ 20 (1/dil)
Time Frame: Day 01, Day 43, Day 202
NT Ab titer ≥ 20 (1/dil) on Day 43; compared to Day 01 and Day 202
Day 01, Day 43, Day 202
Number of participants with NT Ab titer ≥ 40 (1/dil)
Time Frame: Day 01, Day 43, Day 202
NT Ab titer ≥ 40 (1/dil) on Day 43; compared to Day 01 and Day 202
Day 01, Day 43, Day 202
Number of participants with NT Ab titer ≥ 80 (1/dil)
Time Frame: Day 01, Day 43, Day 202
NT Ab titer ≥ 80 (1/dil) on Day 43; compared to Day 01 and Day 202
Day 01, Day 43, Day 202
Geometric mean fold-rise of fold increase in NT Ab titer [post/pre] ≥ 2 and ≥ 4
Time Frame: Day 43
Influenza vaccine antibody titers are measured by serum neutralization (SN) assay
Day 43
Number of participants with detectable NT Ab titer
Time Frame: Day 01, Day 22, Day 43, Day 202
Detectable NT Ab titer: a titer ≥ 10 (1/dil) on Day 01, Day 22, Day 43, Day 202
Day 01, Day 22, Day 43, Day 202

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.
Sanofi

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.
August 3, 2026

Primary Completion (Estimated)

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.
February 22, 2028

Study Completion (Estimated)

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.
February 22, 2028

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).
July 31, 2026

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.
August 19, 2026

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.
August 21, 2026

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.
September 15, 2026

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.
September 11, 2026

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.
September 1, 2026

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.
  • VBX21138
  • U1111-1325-2670 (Registry Identifier: ICTRP)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

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.

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings