广西农村婴儿常规免疫接种及时性地区差异及卫生体系障碍的层次贝叶斯时空模型研究

及时接种是预防儿童传染病的有效方式。影响及时接种的因素既有接种需求方，也有接种提供方、接种政策、可及性等卫生体系因素。前期研究发现麻疹疫苗非及时接种率高的广西农村麻疹发病率也高，且婴儿接种常规免疫疫苗的及时性存在地区差异，但原因不明。鉴于地区间留守婴儿比例、监护人对疫苗接种的知识和信念无差别，我们提出“广西农村婴儿常规免疫接种及时性地区差异可能与卫生体系障碍有关”假设。本研究拟整合空间流行病、现场流行病、定性研究和贝叶斯统计等学科理论，通过生态学研究掌握广西农村婴儿的常规免疫及时接种率及其空间格局；通过空间分层两阶段整群抽样调查和定性研究，测量乡镇、村水平卫生体系因素并评估疫苗接种政策对婴儿及时接种常规免疫的影响；通过层次贝叶斯时空logistic模型和贝叶斯网络模型探索卫生体系因素与接种及时性地区差异的关系，并阐明卫生体系障碍的因果机制。本研究将为优化广西常规疫苗接种策略提供科学依据。

Timely vaccination is the effective way for preventing vaccine-preventable diseases of children. Determinants of timely vaccination are multifactorial, including not only underlying factors of demand-side, but also vaccination-related health system determinants, e.g. supply-side determinants, vaccination policies and accessibility to vaccination services etc. Our previous studies revealed that there was a trend of high-incidence regions having higher coverages of untimely measles vaccination in rural Guangxi, and the geographical disparity in timeliness of routine vaccination among infants was significant. However, the causes underlying the regional difference are still unclear. Given infants mainly live under the care of their parents, and regional differences in the proportion of left-behind infants and level of parents’ knowledge & health belief towards vaccination are not significant in rural Guangxi, we hypothesize that the local vaccination-related health system possibly includes some barriers to causing regional disparity of untimely routine vaccination among infants. In this study, spatial epidemiology, field epidemiology, qualitative study and Bayesian statistics will be integrated. Based on an ecological study, the timely coverages of routine vaccination among rural infants will be evaluated, and the spatial pattern of timely coverages of routine vaccination will be identified at the township scale in rural Guangxi. Through a spatially stratified two-stage cluster sampling survey and qualitative study, vaccination-related health system barriers underlying untimely routine-vaccination will be collected from township-level hospitals, village-level clinics and client side, and in-depth interview and focus group discussion will be conducted to qualitatively assess the impact of the current vaccination related policies on untimely routine-vaccination coverages. Via Hierarchical Bayesian spatio-temporal logistic regression model and Bayesian network model, vaccination-related health system barriers to the timeliness of routine vaccination and causing regional disparity of untimely routine vaccination among infants will be quantitatively identified, and the causal path and causal relationship among significant barriers will be determined. Findings from this study will provide scientific evidence for optimizing routine vaccination-related policies.