2起水痘暴发疫情的病原学和疫苗免疫效果分析

Etiological analysis and evaluation of vaccine efficacy based on two outbreaks of varicella

目的了解深圳市水痘暴发疫情流行病学和病原学特征,开展水痘疫苗人群免疫效果评价。方法选择深圳市2017年2起水痘暴发疫情,开展现场流行病学调查,采集7份疱疹液样本,用聚合酶链式反应扩增水痘-带状疱疹病毒(VZV)ORF62和ORF22片段,比较限制性内切酶NaeⅠ酶切分离株和疫苗株(vOka)ORF62的图谱进行毒株鉴定;将ORF22的PCR产物测序后与NCBI的Dumas株、pOka株和CA123株比较以确定VZV的基因型。结果 2起水痘疫情共有115名病例,平均罹患率为38.6%(115/298),疫情持续时间超过1个月。2起疫情的一剂水痘疫苗接种率分别估计为75.8%~79.4%和62.5%~64.4%,疫苗接种人群的突破性病例发生率各为24.0%(12/50)和29.7%(43/135),疫苗保护率分别为70.0%和57.6%。7份疱疹液样本的ORF62的PCR产物均不被Nae I酶切,均为野毒株。7份样本VZV基因型均为J型。结论深圳市一剂次水痘疫苗接种率不高,突破性病例发生率相对较高,对疫情控制效果有限。未发现疫苗株感染,野毒株为流行毒株,以J基因型为主。

Objective To understand the epidemic and etiological characteristics of varicella outbreaks and evaluate the efficacy of vaccination in Shenzhen.Methods The field epidemic investigation was conducted to illustrate the epidemic characteristics of 2 varicella outbreaks in Shenzhen.Meanwhile herpes specimens were collected from 7 clinically diagnosed cases;ORF22 and ORF62 was amplified respectively by polymerase chain reaction(PCR).The ORF62 PCR products were digested with restricted endonuclease Sma,and then compared with those of vaccine strain vOka to differentiate vaccinestrains from wild-strains.The ORF22 PCR products of wild-strains were sequenced and compared with Dumas(E type,GenBank:X04370.1),pOka(J type,GenBank:AB097933.1)and CA123(M type,GenBank:DQ457052.1)strains in GENEBANK to identify genotype.Results There were 115 varicella cases in 2 outbreaks lasting for more than one month,with an attack rate of 38.6%(115/298).The rate of vaccination was 75.8%~79.4%and 62.5%~64.4%,the incidence of breakthrough cases among vaccinated children was 24.0%(12/50)and 29.7%(43/135),and the vaccine protection rate was70.0%and 57.6%in the 2 outbreaks.7 specimens were wild strains according that the ORF62 PCR products were not digested by Nae I.All the specimens were identified as genotype J.Conclusions The efficacy of varicella vaccination on the disease control was limited because of low vaccinate rate and one dose vaccination in Shenzhen.The wild strain was epidemic,and genotype J was the dominant genotype.