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.

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).

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.