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).
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
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
Parallel
Flu H5 egg pandemic low dose vaccine, with adjuvant
Biological/VaccinePharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Flu H5 Egg Pandemic medium dose vaccine, with adjuvant
Biological/VaccinePharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Flu H5 Egg Pandemic high dose vaccine, with adjuvant
Biological/VaccinePharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Flu H5 Egg Pandemic high dose vaccine, without adjuvant
Biological/VaccinePharmaceutical form: Suspension for injection Route of administration: Intramuscular (IM)
Number of participants with immediate Adverse Events (AEs)
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])
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)
All solicited reactions that are not solicited injection or administration site reactions
Number of participants experiencing unsolicited AEs
Unsolicited AE: an observed AE that does not fulfill the conditions of solicited reactions
Geometric mean titer of hemagglutination inhibition (HAI) assay antibody (Ab) titer obtained on Day 01, Day 22, Day 43, Day 202
Influenza vaccine antibody titers are measured by HAI assay
Geometric mean titer ratio of individual HAI Ab titer ratios Day 22/Day 01, Day 43/Day 01, Day 202/Day 43
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
Number of participants with individual HAI Ab titer ≥ 40 (1/dil) on Day 01, Day 22, Day 43, Day 202
Influenza vaccine antibody titers are measured by HAI assay
Number of participants with seroconversion on Day 22 compared to Day 01 (baseline)
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
