Cross-sectional study on varicella vaccination efficacy in children

[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).Four years after vaccination,antibody in age groups was at the lowest point compared to that of the other groups. [Conclusion] 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.