[Systematic reviews and evidence quality assessment on effectiveness of 1 dose varicella attenuated live vaccine for healthy children aged 1-12 years in China].

Objective: To assess the effectiveness of 1 dose varicella attenuated live vaccine (VarV) for healthy children aged 1-12 years in China and explore the application of the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) framework in observational studies of vaccine effectiveness (VE). Methods: We searched studies about the VE of 1-dose VarV for children aged 1-12 years in China which published before 2019 and evaluated the quality of the studies by the Newcastle Ottawa Scale (NOS) table. We used Meta-analysis models to obtain the pooled 1-dose VE and that in subgroups by study design, outbreak or not, study quality and age of subjects. The evidences of VEs were rated by means of the GRADE system. Results: Thirty-two studies were included and the pooled 1-dose VE was 75% [95% confidence interval (CI): 68%-80%]. The VE of outbreak studies [VE=66% (95%CI: 57%-73%)] was lower than non-outbreak studies [VE=85% (95%CI: 78%-89%)], and the VE in <6 years old children [VE=84% (95%CI:77%-89%)] was higher than that in ≥6 years old children [VE=60% (95%CI: 51%-68%)]. There was no significant difference in VE among studies with different design and quality. The quality of the evidences of pooled 1-dose VE was"very low", which was downgraded in bias risk and inconsistency and not downgraded in indirectness, imprecision and publication bias. Conclusions: The 1-dose VarV can provide medium level protection for 1-12 years old children in China, but it will decrease significantly for ≥6 years old children, so it is suggested to implement the strategies of two-dose vaccination of VarV in children <6 years old. The GRADE framework can be used in the observational studies of VE and it is suggested that the technical guidelines of observational study should be worked out to improve the overall quality of evidence.目的： 系统评价1～12岁健康儿童接种1剂水痘减毒活疫苗保护效果（VE），探索运用GRADE（Grades of Recommendation，Assessment，Development，and Evaluation）证据质量评级方法评价疫苗效果观察性研究。 方法： 检索2019年以前关于中国1～12岁健康儿童1剂水痘减毒活疫苗VE的文献，采用纽卡斯尔-渥太华量表进行文献质量评价，采用Meta分析计算水痘疫苗VE，对研究类型、是否为暴发疫情、文献质量、年龄分亚组计算VE。采用GRADE方法评价整合证据质量。 结果： 共纳入32篇文献，合并后VE值为75%（95%CI：68%～80%），亚组分析暴发疫情VE（66%，95%CI：57%～73%）低于非暴发疫情[85%（95%CI：78%～89%）]，<6岁儿童VE[84%（95%CI：77%～89%）]高于≥6岁儿童VE[60%（95%CI：51%～68%）]，不同研究类型、不同文献质量的VE差异无统计学意义。整合证据评级VE证据质量为"极低"，分别在偏倚风险和不一致性方面降一级，在间接性、不精确性和发表偏倚方面未降级。 结论： 中国1～12岁健康儿童1剂次水痘减毒活疫苗可提供中等水平保护，但≥6岁儿童VE明显降低，建议对<6岁儿童开展2剂次水痘疫苗接种。GRADE的证据质量评级方法可用于疫苗效果的观察性研究，建议制定观察性研究技术指南，提高证据体的整体质量。.