Seroepidemiology of varicella in Hangzhou, China in the vaccine era

Objective To delineate seroepidemiology of VZV in children aged 1-14 years in Hangzhou, to evaluate immunological response of VarV via 2 dose regimen immunization of VarV, for improving immunization strategy of VarV. Methods From 2014-2016, a multi-stage stratified random sampling method was employed to select participants included via physical examination for children in the Community Health Centre in Hangzhou. Results were compared among 11 various age groups: 1-,2-,3-,4-,5-,6-,7-,8-,9-,10-,11-14 years. Demographic data and vaccination history of all subjects derived from Zhejiang Information System for Immunization Program. Then, the second dose of the VarV was conducted on children aged 4-6 years who had immunization history of one dose of VarV. ELISA was used to detect VZV IgG in serum samples. Results 895 subjects with available information were included. The rate of VZV IgG seropositivity was 65.59% and the geometric mean concentration (GMC) for VZV IgG was 5.14 ± 1.89 mIU/ml. The GMC in urban subjects were higher than rural ones. Both the rate of VZV IgG seropositivity and the GMC in children aged 4-6 years groups were statistically lower than participants younger than 4 years and aged 7-14 years (1-,2-,3-,7-,8-,9-,10-,11-14 years). 627 subjects had immunization history of VarV. Both the rate of VZV IgG seropositivity and the GMC in subjects had immunization history of VarV was higher than who had no immunization history.90 subjects were included after the 2nd dose immunization of VarV. Both the rate of VZV IgG seropositivity and the GMC were significantly increased after the immunization of the 2nd dose of VarV. Conclusions The GMC for VZV IgG in children aged 4-6 years were lower than participants groups (1-,2-,3-,7-,8-,9-,10-,11-14 years).2 doses regimen immunization of VarV are effective for increasing both the rate of VZV IgG seropositivity and the GMC in these subjects.