Safety and Immunogenicity of Different Formulations of Monovalent Influenza A/Astrakhan/3212/2020 Like (H5N8) Virus Vaccine With AS03 Adjuvant System in Medically Stable Adults

Inclusion Criteria

• Medically stable participants as established by medical history and clinical examination before entering into the study.
• A male or female >=18 years of age at the time of signing consent form.
• Participants, who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
• Written or witnessed/thumb printed informed consent obtained from the participant prior to performance of any study specific procedure.
• Female participants of childbearing potential or non-childbearing potential may be enrolled in the study if specific criteria are met.

Exclusion Criteria

• Current diagnosis or history of autoimmune disorder(s) except hypothyroidism due to Hashimoto's thyroiditis.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine.
• Clinically significant acute or chronic pulmonary, cardiovascular, hepatic, or renal disease that appears uncontrolled or untreated, as determined by history or physical examination.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history, physical examination, or abnormalities in screening blood tests.
• Recurrent history of or uncontrolled neurological disorders or seizures.
• History of Guillain-Barré syndrome.
• Diagnosed with cancer, or treatment for cancer within 3 years.
• Persons with a history of cancer who are disease-free without treatment for 3 years or more are eligible.
• Persons with a history of histologically confirmed basal cell carcinoma of the skin successfully treated with local excision only, are accepted and are eligible, but other histologic types of skin cancer are exclusionary.
• Women who are disease-free 3 years or more after treatment for breast cancer and receiving long-term prophylaxis are eligible.
• Documented human immunodeficiency virus-positive participants.
• Bedridden participants.
• Personal or family history of narcolepsy.
• Food and Drug Administration (FDA) toxicity Grade 2, or greater, laboratory tests at Screening.
• Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the study.
• Use of any investigational or non-registered product other than the study vaccine during the period beginning 30 days before the first dose of study vaccine (Day -29 to Day 1), or planned use during the entire study period.
• Use of public health emergency vaccines like coronavirus disease 2019 (COVID-19), Monkey pox (mpox) etc. These can be given at any time, but there should a gap of 2 - weeks before a dose of study vaccine can be given.
• Use of any licensed vaccines: prior to receipt of the study vaccine and continuing up to 3 weeks after receiving the dose 2 of study vaccine.
• Administration of long-acting immune-modifying drugs at any time during the study period.
• Administration of immunoglobulins and/or any blood products or plasma derivatives during the period starting 3 months before the first dose of study vaccine or planned administration during the study period.
• Chronic administration of immunosuppressants or other immune-modifying drugs during the period starting 3 months prior to the first vaccine dose and through the entire study period. For corticosteroids, this will mean prednisone equivalent >=20 milligrams/day for 14 days or a total of >=280 mg of prednisone equivalent dose in any 14-day period. Inhaled and topical steroids are allowed.
• Pregnant or lactating female.
• Female planning to become pregnant or planning to discontinue contraceptive precautions within 2 months after completion of the vaccination series.
• History of/or current drug/alcohol abuse.
• Any study personnel or their immediate dependents, family, or household member.
• Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non invest