Incidence pattern of varicella and effect of varicella immunization in Fenghua, Zhejiang,2013

Objective To understand the epidemiological characteristics of varicella and the effect of varicella immunization in Fenghua, Zhejiang province, and provide evidence for the prevention and strategies of varicella. Methods Descriptive epidemiological analysis was conducted on the incidence data of varicella in Fenghua in 2013. The varicella immunization history in age group 1-13 years and the vaccination coverage were surveyed, and age specific protective rates of varicella vaccine were calculated. Results The incidence of varicella was 59.52/lakh. The incidence of varicella in urban area was higher than that in rural area. The incidence was highest in 9-11 yeas age group (1067.05/lakh), followed by age group of 6-8 years (503.21/lakh). The incidence was 19.10% in varicella immunization group (17/89) and 30.00% in control group (3/10) in a varicella outbreak, the difference had no statistical significance. The cases with varicella immunization histories accounted for 61.56% of all varicella cases in age group 1-13 years. The varicella vaccination rate in age group 1-13 years was 72.84%. The overall protective rate of the vaccine was 31.52%, and the protective rates of the vaccine in age groups 1-7 years and 8-13 years were 74.17% and -0.64%, respectively. Conclusion In 2013,varicella mainly occurred in winter in Fenghua. The incidence was high in age group9 years. The protective efficiency of varicella vaccine declined significantly 6 years after the immunization. Due to 1 dose varicella vaccine program, varicella could affect older age group and the outbreak might occur in schools and child care settings. One more dose varicella vaccine should be added in the vaccination program.