Study to Evaluate Immunogenicity, Safety and Tolerability of Adjuvanted and Non-Adjuvanted H2N3 Influenza Vaccines in Adults

Inclusion Criteria: Individuals of 18 years of age and older on the day of informed consent who were not born in 1968. Individuals who have voluntarily given written informed 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, at least 30 days prior to informed consent, which they intend to use for at least 2 months after the last study 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. A body mass index (BMI) ≥35 kg/m2. Progressive, unstable, or uncontrolled clinical conditions as per investigator's assessment. Subjects must be stable and unchanged for a minimum of 3 months. 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 of ≥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 adverse event of special interest (AESI). Received immunoglobulins with immunomodulating effects or any blood products within 180 days prior to informed consent. Received an investigational or non-registered medicinal product within 30 days prior to informed consent. 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 subject 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 the study vaccines. 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 14 days from study vaccination. A known history of Guillain-Barre Syndrome or other demyelinating diseases such as encephalomyelitis and transverse myelitis.