卡介苗在未感染过结核病的儿童中更有效

根据Clinical Infectious Diseases杂志的一项最新研究表明，在未感染过结核病的儿童中接种卡介苗（最好在出生后就立即接种），能够更加有效地抵抗结核病。

　　

生物通报道：根据Clinical Infectious Diseases杂志的一项最新研究表明，卡介疫苗，能比以前认为的更有效地抵抗最常见形式的结核病。

芽孢杆菌卡介苗（BCG）被许多国家列入儿童期免疫接种计划，是唯一一种抵抗结核病（TB）的许可疫苗。然而，人们以前认为，这种疫苗只能有效地抵抗不太常见形式的结核病，这些形式的结核病发生在远离肺部的位置。根据地理位置不同，卡介苗抵抗肺结核（在肺部发现，结核病的最常见形式）的疗效相差很大，范围从印度南部的0%到英国的80%。

为了更好地理解这种变化背后的原因，伦敦卫生与热带医学学院的研究人员，对10种医学电子数据库中报道的所有卡介苗试验的全球文献，做了系统性的回顾和评论，从中寻找影响卡介苗预防肺结核的功效的因素。

这项研究首次表明，卡介苗实际上能够在世界各个地区，高度预防肺结核，包括热带地区接种后出现的明显防护性。

在先前研究中发现的疾病防护上存在的那些表面差异，主要是因为先前的感染减少了疫苗的有效性。那些先前没有结核病传染史的人（包括婴儿）接种卡介苗后，显示出抵抗肺结核的更高功效。

因此，这项研究强调了卡介苗在抵抗肺结核中的一个新作用，需要早期进行疫苗接种，该研究进一步表明，基于卡介苗的结核病新疫苗，也需要在感染发生前进行接种。

本文的第一作者、伦敦卫生和热带医学学院的流行病学临床高级讲师Punam Mangtani博士说：“这项研究，纠正了一个长期存在的误解——卡介苗对抵抗肺部疾病是无效的，证实了卡介苗在控制结核病最常见形式肺结核，和控制所有设置中的传播主源的重要性。由于之前我们知道，感染能够降低疫苗提供的防护，因此，在一个人的一生中尽早接种卡介苗是非常重要的，最好在出生后就立即接种。”（生物通：王英）

生物通推荐原文摘要：
Protection by BCG against tuberculosis: a systematic review of randomised controlled trials
Abstract：
Background. Randomized trials assessing BCG vaccine protection against tuberculosis have widely varying results, for reasons that are not well understood.
Methods. We examined associations of trial setting and design with BCG efficacy against pulmonary and miliary or meningeal tuberculosis by conducting a systematic review, meta-analyses and meta-regression.
Results. We identified 18 trials reporting pulmonary and 6 miliary or meningeal tuberculosis. Univariable meta-regression indicated efficacy against pulmonary tuberculosis varied according to three characteristics. Protection appeared greatest in children stringently tuberculin tested, to try to exclude prior infection with M tuberculosis or sensitisation to environmental mycobacteria (rate ratio [RR] 0.26; 95% CI 0.18-0.37), or infants (0.41; 0.29-0.58). Protection was weaker in children not stringently tested (0.59; 0.35-1.01) and older individuals stringently or not-stringently tested (0.88; 0.59-1.31 and 0.81; 0.55-1.22 respectively). Protection was higher in trials further from the equator where environmental mycobacteria are less and with lower risk of diagnostic detection bias. These associations were attenuated in a multivariable model, but each had an independent effect. There was no evidence that efficacy was associated with BCG strain. Protection against meningeal and miliary tuberculosis was also high in infants (RR 0.1; 95% CI 0.01-0.77) and children stringently tuberculin tested (0.08; 0.03-0.25).
Conclusions. Absence of prior M tuberculosis infection or sensitisation with environmental mycobacteria is associated with higher efficacy of BCG against pulmonary tuberculosis and possibly against miliary and meningeal tuberculosis. Evaluations of new tuberculosis vaccines should account for the possibility that prior infection may mask or block their effects.