| Background:The reported incidence of varicella in Jiangsu Province in 2018 is over 150/100000,among which over 70% are children aged 0-10 years old.Varicella dominates all public health emergencies and has become a growing public health issue in Jiangsu province.At present,varicella vaccine has not been introduced in routine immunization programs in Jiangsu Province,which are given voluntarily at their own expense.At present,there are few studies on the varicella attenuated live vaccine(Var V)coverage of children in Jiangsu province.Many problems should to be solved in the application of 1 dose of Var V,such as the initial immunization age,immunization dose times,epidemic factors,vaccine effectiveness and high incidence of breakthrough cases.Objectives:1.The epidemiological characteristics of varicella in Jiangsu province from 2011 to2018 were analyzed,and the incidence rules of varicella among time,region,population and different occupations were discussed to provide theoretical basis for varicella prevention and control.2.To analyze the vaccination coverage and immune antibody level of Var V for children in Jiangsu Province,and to evaluate the immune effect of the Var V vaccine.3.To explore the epidemic factors of varicella outbreak under high vaccine coverage in school or kindergardens and the vaccine effectiveness of Var V,so as to provide scientific basis for the optimization of varicella immunization strategy.Methods:Descriptive analysis methods were used to describe the epidemiological characteristics of varicella based on case-based disease surveillance information collected by the Chinese infectious disease report information management system.A cross-sectional survey was conducted to collect 3631 serum samples of healthy children aged 1-9 years in some areas of Jiangsu province.Immunoglobulin G(Ig G)antibody levels of varicella were detected by Enzyme-Linked Immunosorbent Assay(ELISA).Questionnaires and vaccination certificates were used to investigate the vaccination coverage of Var V.A 1:2 paired case-control study was conducted to investigate the prevalence of varicella in nurseries and primary schools with high Var V coverage rate in Jiangsu province.Data analysis was performed using conditional logistic regression.Results:1.Epidemiological characteristics of varicella From 2011 to 2018,a total of 317,723 cases of varicella and 2 deaths were reported in Jiangsu Province,with an average reported incidence of 49.81/100,000.The reported incidence rose from 19.27 per 100,000(in 2011)to 160.55 per 100,000(in 2018).The incidence of varicella was bimodal with the first peak from April to June,and the second peak from November to January.The reported incidence was1.19:1 male to female.From 2011 to 2018,the incidence of varicella was mainly in students,accounting for about 70%.In the past eight years,the top three incidence of varicella in Jiangsu province were Wuxi,Zhenjiang and Suzhou.2.Analysis of coverage and antibody level of varicella vaccine In 2016,the reported incidence of varicella in each age group increased compared with the average incidence in 2008-2016.The Var V coverage of healthy children was only 43.5%(95%CI:41.4-45.2%).The seroprevalence after vaccination with one dose of Var V was only 57.1%,the overall seropositivity and GMC were43.1%,225.4 m IU/ml,respectively.The seropositivity of girls was significantly higher than that of boys,and the difference was statistically significant(?2=18.82,P<0.001).The difference in seropositivity between 5-9 age group and 1-4 age group was statistically significant(?2=5.80,P < 0.016).The difference in seropositivity between different regions was statistically significant,with the highest in north area,53.7%(?2=35.64,P<0.001).The seropositivity in one dose of Var V group was significantly higher than that of no immune history group(?2=205.16,P<0.001).3.Varicella epidemic factors and vaccine effectiveness In the outbreak of varicella in primary schools and kindergartens in Jiangsu province,the proportion of breakthrough cases was high(67.7%).Conditional Logistic regression analysis showed that participate in extracurricular training institutions(OR=2.3,95%CI:1.6-3.4),exposure history(OR=1.7,95%CI: 1.1-2.5)and immunization history without Var V(OR=2.7,95%CI: 1.8-4.1)were the main epidemic factors of varicella outbreak.The inoculation duration > 5 years,and the initial immunization age <15 months was potential risk factors for breakthrough cases(all P<0.05).The overall vaccine effectiveness of 1 dose of varicella vaccine was60.3%(95%CI: 40.1-71.9%).Conclusion:In recent years,the incidence of varicella reported a significant upward trend.One dose of varicella vaccine has limited immune effect and is not sufficient to control the spread of the varicella epidemic.The true vaccination coverage rate of varicella vaccine for healthy children in Jiangsu Province is low,and vaccine effectiveness will decrease with increasing age.The vaccine effectiveness of the Var V was better when the initial immunization age was over 15 months.The government should consider a two-dose immunization strategy to better control the occurrence of the varicella epidemic. |
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