NCT07779408 · Sanofi
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.
What this study is about
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.
View original scientific description
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).
Interventions
BIOLOGICAL
Flu H5 egg pandemic low dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
BIOLOGICAL
Flu H5 Egg Pandemic medium dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
BIOLOGICAL
Flu H5 Egg Pandemic high dose vaccine, with adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
BIOLOGICAL
Flu H5 Egg Pandemic high dose vaccine, without adjuvant
Pharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Primary outcome measures
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
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
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
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
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
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
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
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
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
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
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
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
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
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
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.
Where
- Tempe, Arizona
- Rolling Hills Estates, California
- San Diego, California
- Coral Gables, Florida
- DeLand, Florida
- Fort Myers, Florida
- Miami Lakes, Florida
- Decatur, Georgia
- Oak Brook, Illinois
- Newton, Kansas
- Rochester, New York
- North Charleston, South Carolina
And 3 more locations — see the full list below.
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Sep 15, 2026 · Source of record for eligibility and locations