Study to Evaluate Safety and Immunogenicity of Different Priming and Booster Regimens With Adjuvanted H5N8 and/or H5N6 Influenza Vaccine in Adults

Inclusion Criteria: Individuals of ≥18 years of age on the day of informed consent. Individuals who or whose legally acceptable representative(s) have voluntarily given written consent after the nature of the study has been explained according to local regulatory requirements, prior to study entry. Individuals who can comply with study procedures including follow-up. Males, females of non-childbearing potential or females of childbearing potential who are using an effective birth control method which they intend to use for at least 30 days before the first study vaccination and plan to do so until 2 months after the last study vaccination. Individuals must provide a baseline blood sample prior to randomization and vaccination. Exclusion Criteria: Females of childbearing potential who are pregnant, lactating, or who have not adhered to a specified set of contraceptive methods from at least 30 days prior to study entry and who do not plan to do so until 2 months after the last study vaccination. Progressive, unstable or uncontrolled clinical conditions. Hypersensitivity, including allergy, to any component of vaccines, medicinal products or medical equipment whose use is foreseen in this study. Clinical conditions representing a contraindication to intramuscular vaccination and blood draws. Abnormal function of the immune system resulting from: Clinical conditions. Systemic administration of corticosteroids at a dose ≥20 mg/day of prednisone (or equivalent) for more than 14 consecutive days within 90 days prior to informed consent. Topical, inhaled and intranasal corticosteroids are permitted. Intermittent use (one dose in 30 days) of intra-articular corticosteroids are also permitted. Administration of antineoplastic and immunomodulating agents or radiotherapy within 90 days prior to informed consent. History of any medical condition considered an AESI. Received immunoglobulins with immunomodulating effects or any blood products within 180 days prior to informed consent. Individuals who previously received an H5 influenza vaccine or have a known history of H5 influenza infection prior to enrollment. Received an investigational or non-registered medicinal product within 30 days prior to informed consent or are unwilling to refuse participation in another clinical study at any time during the conduct of this study. Study personnel or immediate family or household member of study personnel. Any other clinical condition that, in the opinion of the investigator, might interfere with the results of the study or pose additional risk to the individual due to participation in the study. Individuals who received any other vaccines (with the exception of COVID-19 vaccines) within 14 days (for inactivated vaccines) or 28 days (for live vaccines) prior to enrolment in this study or who are planning to receive any vaccine within 28 days from any of the 3 scheduled study vaccinations. Receipt of any (investigational or licensed) COVID-19 vaccine within 14 days (non-replicating vaccines) or 28 days (replicating vaccines) prior to enrollment or plan to receive any COVID-19 vaccine within 7 days from any of the 3 scheduled study vaccinations. A known history of Guillain-Barre Syndrome or other demyelinating diseases such as encephalomyelitis and transverse myelitis.