Mucosal-specific sIgA antibody GMT;Evaluate the achievement of 2-fold and 4-fold increases in the geometric mean titer (GMT) of specific nasal mucosal sIgA antibodies after vaccination

Inclusion Criteria:

• People aged 3 to 17 years old who voluntarily receive the live attenuated influenza nasal spray vaccine;
• The participant themselves can comply with the protocol requirements and complete sample collection;
• Obtain the consent of the participants' guardians and sign the informed consent form;

Exclusion Criteria:

• Axillary temperature > 37.0°C on the day of enrollment;
• Received any influenza vaccine within the past 2 years and plans to receive other influenza vaccines during the trial period;
• Clinically diagnosed with influenza in a medical institution within the past year (with confirmed etiological diagnosis);
• Individuals with known hypersensitivity to any ingredient contained in this product, including eggs, excipients, and gentamicin sulfate;
• Individuals suffering from acute diseases, severe chronic diseases, acute exacerbations of chronic diseases, and fever;
• Pregnant women;
• Patients with Leigh syndrome who are being treated with aspirin or aspirin-containing medications;
• Individuals with immunodeficiency or those undergoing immunosuppressive therapy;
• Individuals with uncontrolled epilepsy and other progressive neurological diseases, or those with a history of Guillain-Barré syndrome;
• Nasal abnormalities that, in the judgment of a clinician, may affect vaccination, individuals in the medication period for allergic rhinitis, or those currently receiving nasal spray administration;
• Having received a live attenuated vaccine within 14 days prior to enrollment, or a subunit or inactivated vaccine within 7 days prior to enrollment;
• Presence of other factors deemed unsuitable for participation in this study by the investigator.