Abstract: Objective To observe the long term immune effects and its influence factors of 1 dose of Varicella vaccination in children and to explore the strengthening of immunization program.Methods A series of 633 children aged from 12 months to 12 years old were recruited into the study in 2008, who had been injected with 1 dose of imported or domestic Varicella vaccine.From them were collected 629 blood samples from their finger tip blood Varicella medical record tested in 4 blood samples. The level of Varicella IgG antibody was tested by ELISA method. Meanwhile, Varicella vaccination record and varicella disease history were also investigated in the study.Results Mean antibody positivity rate was 69.0% and those of Shanghai native children were much higher than those of children from other provinces (χ²=3.934, P=0.047). Children varicella antibody titers showed a skewed distribution, P₂₅ was 40.19 mIU/mL， P₅₀ was 96.42 mIU/mL，P₇₅ was 290.82 mIU/mL. Antibody on the values for Logarithm were 2.02±0.69 mIU/mL(95%CI:1.97-2.07). Difference in years since vaccination and difference in age groups inoculated on the antibody titer were statistically significant, respectively (F=2.723,P=0.006 and F=3.933,P=0.002).Conclusion Four years after vaccination, antibody in age groups was at the lowest point compared to that of the other groups. Four years after Varicella vaccination, antibody titers in the body dropped to the lowest point,so children were susceptible to Varicella.It is suggested that children should have another 1 dose of VarV four years after the first dose to get more effective immune protection.