Samb B, Aaby P, Whittle H, Seck A M, Simondon F
Unité de Recherche Maladies Infectieuses et Parasitaires, ORSTOM, Dakar, Senegal.
Am J Epidemiol. 1997 Jan 1;145(1):51-7. doi: 10.1093/oxfordjournals.aje.a009031.
The epidemiology of measles has been investigated in Niakhar, a rural area of Senegal, during two periods, 1983-1986 and 1987-1990. Following a major increase in immunization coverage beginning in 1987, the case fatality ratio for all ages declined fourfold from the first to the second period (relative risk (RR) = 0.24, 95% confidence interval (CI) 0.13-0.46). The measles incidence for children under 10 years of age declined by 69% (95% CI 65-72) and the risk of dying of measles by 91% (95% CI 82-95). Vaccinated children who contracted measles had significantly lower case fatality ratio than unvaccinated children with measles (p = 0.038). Children infected by an immunized case tended to have lower case fatality ratio than those infected by an unimmunized index case (p = 0.104) and immunized index cases generated fewer secondary cases than unimmunized index cases (p < 0.001). Respiratory complications were more common in secondary cases infected by an index case with respiratory complications than by an index case without such complications (RR = 1.60, 95% CI 1.08-2.37), which suggests that severe cases give rise to further severe cases. As expected, there was a significant increase in the proportion of vaccinated cases in the second period (RR = 1.41, 95% CI 1.00-1.98). Mean age at infection increased from 4 to 7 years between the two periods and the change in age structure accounted for 20% of the decline in case fatality ratio. Measles immunization may contribute to lower mortality directly through reduced incidence and indirectly through increases in age at infection, less severe infection for immunized cases and changes in transmission patterns leading to reduced severity of measles.
在1983 - 1986年和1987 - 1990年这两个时期，对塞内加尔农村地区尼亚喀尔的麻疹流行病学情况进行了调查。自1987年开始免疫接种覆盖率大幅提高后，各年龄段的病死率从第一个时期到第二个时期下降了四倍（相对危险度（RR）= 0.24，95%置信区间（CI）0.13 - 0.46）。10岁以下儿童的麻疹发病率下降了69%（95% CI 65 - 72），麻疹死亡风险下降了91%（95% CI 82 - 95）。感染麻疹的接种疫苗儿童的病死率显著低于未接种疫苗的麻疹儿童（p = 0.038）。由接种疫苗的病例感染的儿童的病死率往往低于由未接种疫苗的指示病例感染的儿童（p = 0.104），且接种疫苗的指示病例产生的二代病例比未接种疫苗的指示病例少（p < 0.001）。与没有呼吸道并发症的指示病例感染的二代病例相比，由有呼吸道并发症的指示病例感染的二代病例中呼吸道并发症更常见（RR = 1.60，95% CI 1.08 - 2.37），这表明重症病例会引发更多重症病例。不出所料，第二个时期接种疫苗病例的比例显著增加（RR = 1.41，95% CI 1.00 - 1.98）。两个时期之间的平均感染年龄从4岁增加到7岁，年龄结构的变化占病死率下降的20%。麻疹免疫接种可能直接通过降低发病率、间接通过提高感染年龄、使接种疫苗病例的感染不太严重以及改变传播模式导致麻疹严重程度降低，从而有助于降低死亡率。
