Epidemiology of varicella and effect of varicella immunization in Quzhou, Zhejiang, 2006－2014

Objective To understand the epidemiological characteristics of varicella and the effect of varicella immunization in Quzhou, Zhejiang province, and provide evidence for the prevention and control of varicella. Methods Descriptive epidemiological analysis was conducted by using the incidence data of varicella in children in Quzhou during 2006－2014 and the varicella immunization effect in children born after 2005 was evaluated. Results The overall incidence of varicella was 24.12/lakh in children in Quzhou during 2006－2014. The incidence was highest in Kecheng district (87.25/lakh) and lowest in Jiangshan county (2.17/lakh). The incidence peaks were during May-June and during November-January. The incidence in children aged 5－9 years was highest (183.56/lakh), and the incidence in children aged 10-14 years increased with year. The break-through cases with vaccination history accounted for 30.46% in children born after 2005, the vaccination rates increased with year in age group2 years, and the average rates of varicella immunization was 69.93%, the onset time of varicella was delayed effectively by vaccination. The vaccine effectiveness of varicella was 100% within one year after immunization, and declined significantly 6 years after the immunization. Conclusion Varicella outbreak is prone to occur in primary schools. Current 1 dose varicella vaccine immunization strategy can postpone the high incidence of varicella to older age group, but can not prevent the outbreak in collective settings. It is necessary to add one more dose in the immunization.