Inclusion Criteria:
* Age at enrollment is ≥65 years (including the 65th birthday).
* The participant voluntarily agrees to take part in the trial and has signed the informed consent form.
* The participant is able to comply with the trial follow-up schedule as required by the protocol (i.e., no plans for long-term absence or relocation from the study site).
* Medically stable: The participant may have underlying chronic conditions such as hypertension, diabetes, ischemic heart disease, or hypothyroidism, but symptoms/signs must be controlled. If the participant is on any medication, the dosage must have remained stable for at least three weeks prior to vaccination.
Exclusion Criteria:
* Axillary temperature \>37.0°C.
* Confirmed influenza virus infection by laboratory test or self-test kit positive within the past 12 months.
* Received any influenza vaccine (licensed or investigational) within the past 12 months or plans to receive any influenza vaccine during the study.
* Known or suspected allergic to any component of the investigational vaccine.
* A history of severe allergic reactions to any vaccines or medications (for example, but not limited to: anaphylactic shock, allergic laryngeal edema, allergic purpura, thrombocytopenic purpura, local allergic necrotic reaction (Arthus reaction)).
* Congenital malformations or developmental disorders, and genetic defects or severe malnutrition.
* History of convulsions or seizures, epilepsy, psychiatric disorders, or relevant family history.
* Severe liver and kidney diseases, malignant tumors, various acute diseases, or being in the acute exacerbation stage of a chronic disease.
* Diagnosed with congenital or acquired immunodeficiency, HIV infection, lymphoma, leukemia, or other immune-mediated/autoimmune diseases.
* A history of asthma, unstable within the past two years requiring emergency treatment, hospitalization, intubation, or oral/intravenous corticosteroids.
* Individuals who have received immunostimulant or immunosuppressant therapy within the past 6 months (continuously administered orally or via drip infusion for more than 14 days).
* Suffering from severe cardiovascular diseases (e.g., heart disease, cor pulmonale, pulmonary edema).
* Blood pressure ≥150/100 mmHg despite medication control.
* History of live attenuated vaccine within 28 days prior to vaccination, or any other vaccine within 14 days prior to vaccination.
* Diagnosed with progressive neurological diseases, or a history of Guillain-Barré syndrome.
* Asplenia or functional asplenia, including splenectomy due to any reason, or resection/partial removal of other vital organs.
* Received blood or blood-derived products within the past 6 months.
* A diagnosed history of coagulation disorders (e.g., coagulation factor deficiencies, coagulopathies, platelet disorders).
* Currently undergoing anti-tuberculosis treatment.
* Clinically significant abnormalities in laboratory tests (blood biochemistry, blood routine and urine routine) as determined by the investigator.
* Any condition that, in the opinion of the investigator, makes the participant unsuitable for this clinical trial.
