A Study to Find the Dose and Assess the Immune Response and Safety of a Vaccine Against Influenza in Healthy Younger and Older Adults

Inclusion Criteria

• A male or female between and including 18 and 85 years of age (YAs: 18-64; OAs: 65-85) at the time of the study intervention administration.
• Healthy participants or medically stable patients as established by medical history and clinical examination. Participants with chronic medical conditions with or without specific treatment (e.g., chronic metabolic, cardiac, pulmonary, renal, hepatic, neurologic, and hematologic diseases) are allowed to participate in this study if considered by the investigator as medically stable. A stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during 3 months before enrolment.
• Body mass index (BMI) >=18 Kilograms per meter square (kg/m²) and less than or equal to ( ) 5 years before the study intervention administration (excluding effectively treated basal cell skin cancer).
• Any confirmed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination (no laboratory testing required). HIV-infected individuals may be enrolled if they have been stable on antiretroviral therapy for the past 6 consecutive months, i.e., their treatment has not been modified, their cluster of differentiation 4 (CD4) cell count is >= 200/ cubic millimeter (mm³) and their viral load has been undetectable (i.e., HIV-RNA lesser than ( =20 mg/day. Inhaled, intraarticular and topical steroids are allowed.
• Up to 3 months prior to study intervention administration: long-acting immune-modifying drugs including among others immunotherapy (e.g., TNF-inhibitors), monoclonal antibodies, antitumoral medication.
• 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-investigational intervention (drug/invasive medical device).
• Pregnant or lactating female participant.
• Bedridden participants.
• Female participant planning to become pregnant or planning to discontinue contraceptive precautions within the 1-month post-dosing period.
• History of chronic alcohol consumption and/or drug abuse in the past 5 years as deemed by the investigator to render the potential participant unable/unlikely to provide accurate safety reports or comply with study procedures.
• Any study personnel or their immediate dependents, family, or household members.
• Participants with extensive tattoos covering deltoid region on both arms that would preclude the assessment of local reactogenicity.