To evaluate the immunogenicity and safety of 2 doses of quadrivalent influenza virus split vaccine in healthy population aged 6-35 month., so as to provide a data support for phase III clinical trials.

Inclusion Criteria:

• Healthy infants aged 6-35 months.
• Volunteer legal guardian or client informed consent, voluntarily participate in and sign informed consent.
• The volunteer legal guardian or client has the ability (non-illiterate) to understand the study procedures, to use a thermometer, scale, and fill in a diary card as required, and be able to complete the clinical study in compliance with the clinical trial protocol.

Exclusion Criteria:

• The underarm body temperature on the day of enrollment was > 37.0℃.
• Have been suffering from influenza within the previous 3 months (confirmed by either clinical, serological or microbiological methods).
• Any previous influenza vaccination (registered or experimental) within 6 months or any planned influenza vaccination during the study period.
• Allergic to any component of the vaccine, a history of allergic reactions to eggs or gentamicin sulfate.
• A history of severe allergy to any vaccine or drug.
• Preterm birth (delivered before 37 weeks of gestation), low birth weight baby (birth weight < 2300g for girls, <2500g for boys).
• Dystocia, asphyxia rescue, nervous system damage history;
• Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.
• Acute illness, severe chronic illness or acute attack of chronic disease on the day of vaccination;
• A history of live attenuated vaccination within 14 days prior to vaccination and a history of other vaccinations within 7 days prior to vaccination;
• Patients who received immunoenhancement or inhibitor therapy within 3 months (continued oral or intravenous administration for more than 14 days);
• Congenital or acquired immune deficiency, HIV infection, lymphoma, leukemia or other autoimmune diseases;
• History of asthma, past two years of instability requiring emergency treatment, hospitalization, intubation, oral or intravenous administration of corticosteroids;
• Have received blood or blood-related products;
• A history of convulsion, epilepsy, encephalopathy, guillain-barre syndrome, a history of mental illness or a family history;
• A history of abnormal coagulation function (such as coagulation factor deficiency, coagulation disease);
• Planning to relocate before the end of the study or to leave for an extended -period during the scheduled study visit;
• Participating in or planning to participate in other clinical trials in the near future;
• The investigators determined that any conditions were inappropriate to participate in the clinical trial.