The purpose of this study is to evaluate the protective effect, safety and immunogenicity of a live attenuated varicella vaccine in healthy children.

This study is a randomized, blind, controlled phase III clinical trial. The purpose of this study is to evaluate the protective effect, safety and immunogenicity of a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd. The control is diluent of lyophilized vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd. All participants are healthy, and will be randomly assigned into experimental group or control group in the ratio 1:1.

Inclusion Criteria:

• Healthy volunteer between 1 - 12 years old;
• Proven legal identity;
• Guardian(s) of the volunteer and/or volunteers themselves should be capable of understanding the written consent form, and such form should be signed before the volunteer being included into this study;

Exclusion Criteria:

• Prior vaccination with varicella vaccine or with history of varicella zoster virus (VZV) infection;

• Axillaty temperature > 37.0 °C;

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

• History of epilepsy, seizures or convulsions, or a family history of mental illness, autoimmune disease or immunodeficiency;

• Severe malnutrition, congenital malformation, developmental disorders, or serious chronic diseases;

• Acute disease or acute stage of chronic disease within 7 days prior to study entry;

• Receipt of any of the following products:

  1. Any subunit vaccine or inactivated vaccine within 7 days prior to study entry;
  2. Any live attenuated vaccine within 1 month prior to study entry;
  3. Any blood product, immunosuppressant, hormone, or other investigational medicine(s) within 30 days prior to study entry;

• Any significant abnormity of heart, lung, skin, or pharynx;

• Any other factor that suggesting the volunteer is unsuitable for this study based on the opinions of investigators;