The purpose of this study is to gather additional evidence of the safety and immunogenicity of 1 dose of Fluarix Tetra (0.5 milliliter [mL]) (Northern Hemisphere (NH)2023-2024) in individuals aged 65 years and above to fulfill a post-approval condition imposed by the Indian regulatory authorities (CDSCO) for this age group in India.

Inclusion Criteria:

• Male or female participants aged >= 65 years of age
• Participants and/or legally acceptable representative (s) (LAR) who in the opinion of the Investigator, can and will comply with the requirements of the protocol (e.g., completion of the diary cards, return for follow-up visits
• Written or witnessed/thumb printed informed consent obtained from the participant and/or participant's LAR(s) after the study has been explained according to the local authority requirements and prior to performance of any study-specific procedure

Exclusion Criteria:

• History of severe allergic reactions (e.g., anaphylaxis) to any component of the vaccine, including egg protein, or following a previous dose of any influenza vaccine.
• Receipt of licensed vaccine, immune sera and/or any blood products, or an investigational trial agent within previous 30 days or planned during their participation in the trial.
• Receipt of any flu vaccine within 6 months before trial start or any other vaccine within 30 days before the trial.
• Receipt of any dose of a Coronavirus Disease 2019 (COVID-19) vaccine within 15 days of trial start.
• History of Guillain-Barré Syndrome.
• Altered immune status or chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying agents within six months prior to administration of trial vaccine.
• History of acute infectious disease or acute respiratory illness needing antibiotics or antivirals in the previous 7 days, based on investigator's judgement.
• If a participant candidate has fever, the trial vaccination should be postponed to when the fever has resolved for at least 2 days (temporary exclusion criterion). Fever is defined as temperature >=38.0 degree Celsius (°C) (100.4 degrees Fahrenheit [°F]) by any route. The preferred location for measuring temperature will be oral route.
• Acute or chronic clinically significant pulmonary, cardiovascular, hepatic, or renal functional abnormality, as determined by medical history, physical examination, or laboratory screening tests.
• Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the trial.

IPD for this study will be made available via the Clinical Study Data Request site.

IPD will be made available within 6 months of publishing the results of the primary endpoints, a key secondary endpoints and safety data of the study.

Access is provided after a research proposal is submitted and has received approval from the Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension can be granted, when justified, for up to another 12 months.