The purpose of this study is to evaluate the safety and immunogenicity of quadrivalent influenza vaccine in healthy children aged 6-35 months.

The study includes open-labelled phase I and randomized, double-blind, controlled phase III clinical trial. In the phase I, 20 healthy Chinese children aged 6-35 months were administered with two doses of QIV (7.5μg/0.25ml). In the phase Ⅲ clinical trial, 2320 children were assigned to QIV group, TIV (B/Victoria) group and TIV (B/Yamagata) group in a 2:1:1 ratio. All vaccines were manufactured by Sinovac Biotech Co., Ltd.

Inclusion Criteria:

• Healthy volunteer between 6 - 35 months old; Term birth; Birth weight >2500g;
• Proven legal identity;
• Written consent of the guardian(s) of the volunteer;

Exclusion Criteria:

• Received seasonal influenza vaccine in the current year;

• Suffering from seasonal influenza in the past 6 moths;

• Axillaty temperature > 37.0 °C;

• History of allergy to any vaccine or vaccine ingredient;

• History of serious adverse reaction(s) to vaccination, such as urticaria, difficulty in breathing, angioneurotic edema, abdominal pain, etc;

• Autoimmune disease or immunodeficiency;

• Congenital malformation, developmental disorders;

• Severe malnutrition;

• Diagnosed coagulation function abnormal (e.g., coagulation factor deficiency, coagulation disorder, or platelet abnormalities) , or obvious bruising or coagulation disorders;

• History of epilepsy (except febrile seizures occurred < 2 years of age or pure epilepsy occurred within the past 3 years that does not need treatment)

• Chronic diseases (e.g., viral hepatitis, tuberculosis, diabetes, blood diseases, or neurological disorders)

• Acute disease or acute stage of chronic disease;

• Receipt of any of the following products:

  1. Any subunit vaccine or inactivated vaccine (e.g., pneumococcal vaccine) or treatment of allergy within 14 days prior to study entry;
  2. Any live attenuated vaccine within 30 days prior to study entry;
  3. Any other investigational medicine(s) or vaccine within 30 days prior to study entry;
  4. Blood product within 3 months prior to study entry;
  5. Any immunosuppressant, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) within 6 month prior to study entry;

• Participate or will participate in other clinical trial(s) during this study;

• Based on the judgment of investigator(s) or the Ethic Committee, there was any condition indicating that the subject should be excluded;