广西农村25-36月龄儿童及时、全程麻疹疫苗接种率及多水平模型研究

Measles is a major infectious disease caused by morbilli virus. Timely & complete measles vaccination is the effective way for preventing measles. During 2013 to 2014 years, large-scale outbreak occurred in Baise, Hechi and Nanning prefecture of Guangxi. And most of the reported cases were scattered children in rural areas. However, the causes underlying this outbreak are still unclear. Our previous studies revealed the reported coverage rates of 1st dose of measles vaccine were over 95% during 2007-2014 years, as well as the reported coverage rates of 2nd dose of measles vaccine. It should be noted that higher reported coverage rate of measles vaccination does not mean higher timely measles vaccination, since reported coverage rate may mask the substantial delays in vaccination and subsequent lack of immunity. Accordingly, we hypothesize the outbreak of measles in Guangxi may be due to the delay & incomplete measles vaccination. In this study, qualitative study (study on measles vaccination policy) , quantitative study (survey on timely & complete measles vaccination rate), spatial statistics, multilevel statistics, and GIS will be integrated. Through a stratified two-stage systematic random sampling study with PPS (probability proportion to sample size), the timely & complete measles vaccination rates for Guangxi rural children aged 25-36 months will be evaluated, which may assist in exploring the cause of measles outbreak in areas of Guangxi where the reported measles coverage rate was quite high. Via multilevel binary logistic regression model and multilevel structural equation model, determinants of failure to receive timely & complete measles vaccination among Guangxi rural children will be explored at the family level, village level and township level, which will provide scientific evidence for optimizing measles vaccination policy.

麻疹是由麻疹病毒引起的重大传染病。预防麻疹有效的方式是及时、全程接种麻疹疫苗。2013-2014年，麻疹相继在广西河池、百色、崇左和南宁暴发，以≤2岁农村儿童为主，暴发原因不清楚。前期研究发现广西麻疹疫苗第一针、第二针的报告接种率近八年来均在95%以上。报告接种率高不等于发病率低，报告接种率可能掩盖了接种的及时性。因此，我们提出“广西麻疹暴发可能与麻疹疫苗及时、全程接种率不高有关”假设。本研究拟交叉融合现场流行病学、多水平统计模型、空间统计学、定性研究和GIS空间分析等学科理论，通过分层两阶段PPS抽样研究测算广西农村25-36月龄儿童的及时、全程麻疹疫苗接种率，揭示广西麻疹暴发的原因；通过（多元）多水平（空间）logistic模型和多水平结构方程模型探索家庭、村和乡镇水平因素与儿童延迟、非全程接种麻疹疫苗的关系，阐明它们之间的机制。本研究将为优化广西麻疹疫苗接种策略提供科学依据。

1. 项目背景. 预防麻疹有效的方式是及时、全程接种麻疹疫苗。2013-2014年，广西农村儿童出现大规模麻疹暴发，原因尚不清楚。监测数据显示广西MCV1、MCV2报告接种率均在95%以上。这提示报告接种率高不等于发病率低，报告接种率可能掩盖了接种的及时性。因此，我们提出“广西农村麻疹暴发可能与麻疹疫苗及时、全程接种率不高有关”假设。.2. 主要研究内容. 项目主要研究内容包括广西农村儿童的及时、全程麻疹疫苗接种率，广西农村儿童非及时全程接种麻疹疫苗的政策影响因素，广西农村儿童非及时接种麻疹疫苗的多水平统计模型等3个部分。第一部分为分层三阶段整群抽样横断面研究，第二部分为接种政策定性研究，第三部分为家庭、村、乡镇水平因素的多水平（空间）Logistic模型研究。.3. 重要结果、关键数据及科学意义. 横断面研究主要发现广西农村儿童MCV1及时接种率为58.4%, MCV2及时接种率为76.9%, MCV1 & MCV2的及时、全程接种率为47.4%。MCV1的中位延迟接种期为32天，MCV2的中位延迟接种期为159天。麻疹发病率高的地区其麻疹疫苗不及时接种率也高、中位延迟接种期也长。这提示麻疹疫苗报告接种率高掩盖了接种的及时性，广西麻疹暴发可能与当地麻疹疫苗及时、全程接种率不高有关。. 定性研究主要发现预防接种人力资源不足，缺经济激励措施，接种经费使用程序复杂，卫生院集中接种模式的运行方式缺灵活性，防保人员对接种及时性不满意。结果表明当前疫苗接种相关政策对广西农村儿童获得及时、全程麻疹疫苗接种服务具有一定的负面影响，麻疹疫苗接种率高的广西农村地区再现大规模麻疹暴发可能与这些政策背景有关。. 多水平模型发现影响儿童非及时接种麻疹疫苗服务的家庭因素主要有健康监护人的疫苗接种知识水平差、接种健康信念薄弱、接种实践积极性不高、接种服务满意度低；村级因素主要有村医不参与常规免疫接种服务、到乡镇卫生院的出行时间长；乡镇因素主要有乡镇卫生院不提供书面接种通知单、每月常规免疫接种服务日数量不足、常规免疫接种服务日分布不均、非圩日接种、防保人员配置未达标，乡镇卫生院无专职疫苗接种小组。

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