a clinical trial of quadrivalent influenza vaccine in children aged 3-8 years old

Conditions: Seasonal Influenza

Summary: this is an open-label, randomized and controlled phase ⅳ clinical trial of quadrivalent influenza vaccine manufactured by sinovac biotech co. , the purpose of this study is to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine with that of 2 doses in vaccine-unprimed children aged 3-8 years old,to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children and to compare the immunogenicity and safety after 2 doses of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children.

this study is open-label, randomized and controlled phase ⅳ clinical trial of quadrivalent influenza vaccine.the purpose of this study is to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine with that of 2 doses in vaccine-unprimed children aged 3-8 years old,to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children and to compare the immunogenicity and safety after 2 doses of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children.a total of 600 subjects including 400 vaccine-unprimed children and 200 vaccine-primed children will be enrolled,400 vaccine-unprimed children will be randomly divided into two groups in a 1:1 ratio.subjects in group 1(experimental group 1 ) will receive two doses of quadrivalent influenza vaccine on the immunization schedule of day 0,28 and subjects in group 2 (experimental group 2) will receive one dose of quadrivalent influenza vaccine.200 vaccine-primed children (experimental group 3) will receive one dose of quadrivalent influenza vaccine.

Eligibility criteria:
vaccine-unprimed children inclusion criteria: * healthy children aged 3-8 years; * the subjects' guardians can understand and voluntarily sign the informed consent form; * proven legal identity. exclusion criteria: * received any circulating seasonal influenza vaccine prior to enrollment or had an influenza vaccine schedule during the study; * suffering from seasonal influenza in the past 6 moths; * history of asthma, history of allergy to the vaccine or vaccine components, or serious adverse reactions to the vaccine, such as urticaria, dyspnea, and angioedema; * congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.; * autoimmune disease or immunodeficiency / immunosuppression; * severe chronic diseases, severe cardiovascular diseases, hypertension 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; * thyroid disease or history of thyroidectomy, asplenia,functional asplenia, asplenia or splenectomy resulting from 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; * history of drug abuse; * receipt of blood products within in the past 3 months; * receipt of other investigational drugs in the past 30 days; * receipt of inactivated or subunit vaccines in the past 7 days; * acute diseases or acute exacerbation of chronic diseases in the past 7 days; * axillary temperature \>37.0°c; * according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial. vaccine-primed children inclusion criteria: * healthy children aged 3-8 years; * the subjects' guardians can understand and voluntarily sign the informed consent form; * proven legal identity; * received at least 1 dose of seasonal influenza vaccine in previous epidemic seasons exclusion criteria: * received an seasonal influenza vaccine for the current epidemic season (2020-2021 epidemic season) prior to enrollment, or had an influenza vaccine schedule during the study; * suffering from seasonal influenza in the past 6 moths; * history of asthma, history of allergy to the vaccine or vaccine components, or serious adverse reactions to the vaccine, such as urticaria, dyspnea, and angioedema; * congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.; * autoimmune disease or immunodeficiency / immunosuppression; * severe chronic diseases, severe cardiovascular diseases, hypertension 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; * thyroid disease or history of thyroidectomy, asplenia, functional asplenia, asplenia or splenectomy resulting from 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; * history of drug abuse; * receipt of blood products within in the past 3 months; * receipt of other investigational drugs in the past 30 days; * receipt of attenuated live vaccines in the past 14 days; * receipt of inactivated or subunit vaccines in the past 7 days; * acute diseases or acute exacerbation of chronic diseases in the past 7 days; * axillary temperature \>37.0°c; * according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.