Research on BCG vaccination.

BCG vaccination against tuberculosis has been used for many years in practically all national tuberculosis programmes. It is often the mainstay of the programme as regards young children, in whom case-finding and treatment remain deficient, especially regarding the serious meningeal and miliary forms of tuberculosis. Following contradictory reports on the effectiveness of BCG vaccination, a large-scale controlled trial was carried out in south India, under the sponsorship of WHO. The early results of this trial showed that BCG vaccination provided no protection whatsoever against bacillary disease in adults. To examine this unexpected finding WHO convened a Scientific Group, which considered that the reported results per se are valid but might not apply in general. Since the effectiveness of a potentially very useful and generally applied control measure appeared seriously challenged, a Study Group was convened by WHO. The Group considered that under the circumstances BCG vaccination, especially of young children, should be continued, but that the effectiveness of BCG vaccination should be evaluated forthwith. A comprehensive programme has been formulated accordingly. The primary objective of the programme is to evaluate in an expedient manner the effectiveness of BCG vaccination in children. A number of problems inherent to the special situation had to be circumvented. In the case of tuberculosis, community trials of the classical type have to be prolonged and are extremely costly. Moreover, since BCG vaccination has been used widely, it is virtually impossible to find a suitable trial area; many countries are reluctant to conduct such trials for ethical reasons because they require an unvaccinated group. Retrospective studies, although providing no conclusive scientific evidence when carried out in isolation, may give useful information if organized in a comprehensive evaluation programme. Another approach proposed is based on the active follow-up of child contacts of newly detected cases of tuberculosis. This provides information on the magnitude of the tuberculosis problem in children as well as a powerful retrospective evaluation of the protective effect of vaccination; in the case that the results are inconclusive a prospective approach on the same principle would be ethically justified. The study population is only a small fraction of that required in a community trial, and the follow-up of each individual is reduced to a few months. In addition to providing information on the effectiveness of BCG vaccination, the field studies, supported by other research, may clarify the variations in protection observed.(ABSTRACT TRUNCATED AT 400 WORDS)