Styblo K, Meijer J
Tubercle. 1976 Mar;57(1):17-43. doi: 10.1016/0041-3879(76)90015-5.
There is general agreement that BCG vaccination with a potent strain, when given to previously uninfected subjects, is highly effective in preventing the development to tuberculosis among them. This "direct" effect may be measured in practice in terms of the proportion of cases prevented in the age-groups in which the vaccination has been made. It is also clamined that mass BCG vaccination-especially at school-leaving age-can be expected to yield benefits not only directly, but also indirectly, by breaking the chain of transmission and so preventing the development of tuberculosis in unvaccinated subjects. This "indirect" effect may be measured, by analogy, in terms of the reduction in the numbers of cases in the age groups in which no vaccinations have been performed (the older age groups, and also young children, if BCG vaccination is given, for instance, to school-leavers). The indirect effect will be observed in terms of changes in both smear-positive and smear-negative cases. However, because smear-positive cases are the principal sources of infection, it is more meaningful to measure the indirect effect in terms of the reduction in the numbers of smear-positive (infectious) cases. The present paper falls into three parts: I. A comparison of the trends in the incidence of infectious tuberculosis in Norway, Denmark and The Netherlands. The study confirms that the substantial direct effect of BCG vaccination on the total tuberculosis incidence, which was shown by Bjartveit and Waaler, also applies to the incidence of infectious tuberculosis. II. A comparison of the trends in the incidence of infectious tuberculosis in the three countries and in different age groups over 30, and in the incidence of all forms of tuberculosis in children, in whom BCG vaccination has not been used. These comparisons suggest that the indirect effect of BCG on infectious cases of tuberculosis in persons aged 30 years and over, and on all forms of tuberculosis in children, in whom BCG vaccination has not been used, is not readily detectable, and so may not be large. However, the trends in tuberculosis incidence measure the total effects of all the policies for control used in the three countries under study. The comparisons between the three countries can therefore not isolate the "pure" direct and indirect effects of BCG from the effects of other differences between the control policies. For this reason a theoretical study of the problem has been made. III. A theoretical examination of the maximum likely indirect effect of a mass BCG vaccination policy in diminishing the prevalence of sources of infection in the population. This shows that the effect of BCG in preventing smear-positive cases in developing countries (if a constant risk of infection of about 3 per cent is presumed), is between 0.3 per cent and 2.0 per cent per year. This effect depends mainly upon the efficacy of BCG vaccine, the population covered and the duration of protection from BCG vaccination...
人们普遍认为，给以前未感染过的人群接种高效菌株的卡介苗，在预防他们患结核病方面非常有效。这种“直接”效果在实际中可以通过接种疫苗的年龄组中预防病例的比例来衡量。还有人声称，大规模卡介苗接种——尤其是在离校年龄时接种——不仅有望直接产生益处，还能通过打破传播链从而预防未接种疫苗人群患结核病，间接产生益处。这种“间接”效果可以类推，通过未接种疫苗的年龄组（年龄较大的组，以及如果例如给离校学生接种卡介苗，幼儿组）中病例数的减少来衡量。间接效果将通过涂片阳性和涂片阴性病例的变化来观察。然而，由于涂片阳性病例是主要的传染源，从涂片阳性（传染性）病例数的减少来衡量间接效果更有意义。本文分为三个部分：一、挪威、丹麦和荷兰传染性结核病发病率趋势的比较。该研究证实，比雅特维特和瓦勒所显示的卡介苗接种对总结核病发病率的显著直接效果，也适用于传染性结核病的发病率。二、这三个国家与30岁以上不同年龄组的传染性结核病发病率趋势，以及未使用卡介苗接种的儿童中所有形式结核病发病率的比较。这些比较表明，卡介苗对30岁及以上人群的传染性结核病例以及未使用卡介苗接种的儿童中所有形式结核病的间接效果不易察觉，因此可能不大。然而，结核病发病率趋势衡量了所研究的这三个国家使用的所有控制政策的总体效果。因此，这三个国家之间的比较无法将卡介苗的“纯粹”直接和间接效果与控制政策的其他差异的效果区分开来。出于这个原因，对该问题进行了理论研究。三、对大规模卡介苗接种政策在降低人群中传染源流行率方面最大可能的间接效果的理论研究。这表明，在发展中国家（如果假定感染风险恒定约为3%），卡介苗预防涂片阳性病例的效果每年在0.3%至2.0%之间。这种效果主要取决于卡介苗疫苗的效力、覆盖的人群以及卡介苗接种提供的保护持续时间……
