The purpose of this study is to evaluate the safety and immunogenicity of Influenza vaccine (Split virion), Inactivated, Quadrivalent developed by Sinovac Biotech Co., Ltd. (Sinovac-QIV) as compared to a licensed comparator in Chile and Philippines, Vaxigrip Tetra™ (Vaxigrip Tetra-QIV) in individuals aged 3 years and older.

This study is a phase Ⅲ, double-blind, randomized and active-controlled clinical trial to evaluate the safety and immunogenicity of Influenza vaccine (Split virion), Inactivated, Quadrivalent developed by Sinovac Biotech Co., Ltd. (Sinovac-QIV) as compared to a licensed comparator in Chile, Vaxigrip Tetra™ (Vaxigrip Tetra-QIV) in individuals aged 3 years and older. Subjects will be randomized 1:1 to received either Sinovac-QIV or Vaxigrip Tetra-QIV. Vaccine-primed subjects will receive one 0.5ml dose of Sinovac-QIV or Vaxigrip Tetra-QIV on day 0. Vaccine-unprimed subjects will receive two 0.5ml doses of Sinovac-QIV or Vaxigrip Tetra-QIV and day 0 and day 28, respectively. Subjects who are 3-8 years of age had prior receipt of ≥2 doses of influenza vaccine at least 4 weeks apart or who are ≥9 years old are considered "vaccine-prime". Subjects who are 3-8 years of age had prior receipt of <2 dose of influenza vaccine are considered "vaccine-unprimed".

Inclusion Criteria:

• Volunteers age 3 years and older, in good health or medically stable;

• Written informed consent obtained from subjects or/and legal guardian;

• No receipt of influenza vaccines within 6 months or plans to receive any influenza vaccines during the study;

• Female subjects of non-child bearing may be enrolled in the study. Non-child bearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or premenarche or postmenopausal (defined as amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause);

• Female subjects of child bearing potential may be enrolled in the study, if the subject

  • Has a negative pregnancy test on the day of the first dose (day 0);
  • Has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first dose and until at least 28 days after vaccination.

Exclusion Criteria:

• History of seasonal influenza within 6 months prior to the study entry;
• Axillary temperature ≥37.3℃;
• History of Guillain-Barré syndrome within 6 weeks of receipt of prior influenza vaccine;
• History of allergy to any vaccine, or any ingredient of the experimental vaccine;
• Serious adverse reaction(s) to the vaccine, such as urticaria, dyspnea or angioneurotic edem etc.;
• History of serious neurological disorder (such as epilepsy, convulsions etc.) or a mental illness;
• Autoimmune disease or immunodeficiency/immunosuppressive, or any immunosuppressant receipt within 6 months prior to the study entry;
• Significant chronic illnesses that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion (may include, but are not limited to cardiovascular disease, hypertension and diabetes that cannot be controlled by drugs, liver or kidney disorders, HIV infection or malignant tumor;
• Acute central nervous system diseases such as encephalitis/myelitis, acute disseminating encephalomyelitis, and related disorders;
• Absence of spleen, functional absence of spleen, and absence or removal of spleen under any circumstances;
• Diagnosed coagulation function abnormal (e.g., coagulation factor deficiency, coagulation disorder, or platelet abnormalities), or obvious bruising or coagulation disorders;
• Alcoholism or history of drug abuse；
• Acute disease or acute stage of chronic disease within 7 days prior to study entry;
• Received blood products within 3 months prior to study entry;
• Received any live attenuated vaccine within 14 days prior to study entry or any subunit vaccine or inactivated vaccine within 7 days prior to study entry;
• Pregnant women or lactating women;
• Subjects participate other clinical trials (licensed or unlicensed vaccines, drugs, organisms, devices, blood products or drugs) during the study period;
• Any other factors which are unsuitable for participation in the clinical trial as judged by the investigator.