This is an open-labelled clinical trial of live attenuated varicella vaccines manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd .The purpose of this study is to evaluate the immunity persistence of the single-dose primary immunization of live attenuated varicella vaccine on different time points ,and the safety and immunogenicity after the booster immunization

This study is an open-labelled phase Ⅲ clinical trial.The experimental vaccine manufactured by Sinovac(Dalian) Vaccine Technology Co., Ltd.A total of 1195 subjects who received vaccine in the phase Ⅲ lot-consistency clinical trial were be enrolled .All subjects except C0243 and C0556 were divided into 3 groups according to the order of study number.Subjects in 3 groups received a booster immunization of live attenuated varicella vaccines 1 year,2 years and 3 years after primary immunization,respectively.About 3.0ml of venous blood was collected from each enrolled subject at pre-booster immunization,30 days after booster immunization and the serum was separated for neutralizing antibody detection.The antibody levels were used to evaluate the immunity persistence and immunogenicity after booster immunization of live attenuated varicella vaccines .

Inclusion Criteria:

• Received one dose live attenuated varicella vaccine in the phase Ⅲ lot-consistency clinical trial;
• Guardian(s) of the volunteer should be capable of understanding the written - consent form, and such form should be signed before the children being included into this study.

Exclusion Criteria:

• Received one dose live attenuated varicella vaccine at the end of the phase Ⅲ lot-consistency clinical trial;
• According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.