This study is a randomized, double-blind phase Ⅳ clinical trial of quadrivalent influenza vaccine (Split Virion), inactivated manufactured by Sinovac Biotech Co., Ltd.The purpose of this study is to evaluate the lot-to-lot consistency, immunogenicity and safety of quadrivalent influenza vaccine (Split Virion), inactivated in health subjects aged 9-59 years old.

This study is a randomized, double-blind phase Ⅳ clinical trial in health subjects aged 9-59 years old to evaluate the lot-to-lot consistency,immunogenicity and safety of quadrivalent influenza vaccine (Split Virion), inactivated.The experimental vaccine was manufactured by Sinovac Biotech Co., Ltd.A total of 1260 subjects,including 360 subjects aged 9-17 years and 900 subjects aged 18-59 years will be enrolled.The subjects in each age group will be randomly divided into three groups in a ratio of 1:1:1 to receive one dose of three lots of quadrivalent influenza vaccine (Split Virion), inactivated produced on a commercial scale,respectively.

Inclusion Criteria:

• Healthy subjects aged 9-59 years;
• The subjects and/or guardians can understand and voluntarily sign the informed consent form (For subjects aged 9-17 years, both subjects and guardians need to sign the informed consent form).
• Proven legal identity.

Exclusion Criteria:

• Received seasonal influenza vaccine for 2022-2023 influenza season, or had an influenza vaccine schedule during the study;
• Suffering from seasonal influenza in the past 6 moths;
• Women of childbearing age (menarche to premenopause) are pregnant(including positive urine pregnancy test), breastfeeding or planning pregnancy within 1 month;
• Patients with fever on the day of vaccination,underarm body temperature>37.2 ℃;
• History of asthma, allergy to vaccines or vaccine components, and serious adverse reactions to vaccines, such as urticaria, dyspnea, and angioneurotic edema;
• Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.
• Severe chronic diseases,such as severe cardiovascular diseases, hypertension(Systolic blood pressure ≥140mmHg and/or diastolic blood pressure ≥90mmHg) and diabetes that cannot be controlled by drugs, liver or kidney diseases,malignant tumors, etc.;
• Severe neurological disease (epilepsy, convulsions or convulsions) or mental illness;
• Autoimmune disease or immune deficiency/immunosuppression;
• Thyroid disease or history of thyroidectomy,absence of spleen, functional functional asplenia,and absence of spleen or splenectomy as a result of any condition;
• Diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation;
• Immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids(excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months;
• A long history of alcohol or drug abuse;
• Onset of various acute or chronic diseases within 7 days prior to the study;
• Receipt of blood products within in the past 3 months;
• Receipt of other investigational drugs within 30 days prior to receiving the investigational vaccine;
• Receipt of attenuated live vaccines or COVID-19 vaccines in the past 14 days,receipt of inactivated or subunit vaccines in the past 7 days;
• The subjects participated in other clinical trials during the follow-up period or will be planned to participate other clinical trials during the follow-up period;
• According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.