目的：结核病的发病率近年有所回升，临床对结核病的治疗研究较多，但卡介苗接种后对机体的保护作用如何，持续时间长短，何时复种等研究不多。鉴于此，该文研究卡介苗接种对儿童的保护作用。方法：对该市城乡9608例0～14岁接种卡介苗(简称种卡)的儿童进行卡痕、PPD试验(结核菌纯蛋白衍化物)普查。结果：3个月～组小儿PPD阳性率最高，为 91.5%；1岁～ 组次之，为 81.6%；3岁～组最低，为 57.1%；7～14岁组PPD阳性率又有回升，为 74.2%，各组间差异有显著性(P<0.01)。城市儿童PPD阳性率为 78.8%，高于乡村儿童( 62.4%)；卡痕阳性率为 90.3%，高于乡村儿童(56.1%)，P<0.01；结核 自然感染率低于乡村儿童(1.7% vs 3.4%)，P<0.05。<3岁儿童结核自然感染率最低(0.5%)，低于3～7岁和7～14岁，7～14岁儿童自感率最高。结论：卡介苗对0～3岁儿童保护作用明显，对4岁以上儿童保护作用渐减弱；且城市儿童PPD阳性率和卡痕阳性率明显高于乡村儿童，说明种卡质量值得重视。

OBJECTIVE: The incidence of tuberculosis (TB) has begun to rise again in the world in recent years. Reseachers have focused mainly on treatment for TB but have seldom studied on protective effect of vaccination of bacillus calmette guerin (BCG) on children. The aim of this study was to investigate the protective duration and impact of vaccinating children with BCG. METHODS: The BCG scar rate and positive purified protein derivative (PPD) rate were studied in 9 608 children who were vaccinated in both the urban and rural areas of Xianning City and who ranged in age from 0 to 14 years. RESULTS: The positive PPD rate of the children between 3 months and 1 year was the highest ( 91.5% ); it was the second highest in children ranging from 1 to 3 years ( 81.6% ), the lowest in children ranging from 3-7 years ( 57.1% ) and rose again in children ranging from 7-14 years ( 74.2% ) (P< 0.01 ). The positive PPD rate of the urban children was higher than that of the rural children ( 78.8% vs 62.4% ); the positive BCG scar rate of the urban children was 90.3% , higher than that of the rural children ( 56.1% ) (P< 0.01 ). The inciderce of natural TB infection in urban children was lower than that of the rural ones ( 1.7% vs 3.4% ). The incidence of natural TB infection in the children between 3 months to 3 years old was higher than those of the children raning from 3-7 years and 7-14 years. It was the highest in the children ranging fro 7 to 14 years.CONCLUSIONS: The protective effect of the BCG vaccination on 0-3 year old children is significant, but reduces on children of 4 years of age or older. The positive PPD rate and BCG scar rate of the urban children were higher than those of the rural children, indicating that the quality of vaccination of BCG should be improved in rural areas.