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。

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.