BCG vaccination and epidemiological situation: a decision making approach to the use of BCG.

The clinical efficacy of a well-controlled and correctly applied BCG vaccine can hardly be questioned, nor its usefulness under individual circumstances. But a problem more and more often raised now is that of the opportuneness, at the present time, to still use BCG on a mass- systematic - scale, particularly in the TB control programmes of low-prevalence countries. The article proposes an approach which, alongside with other methods already presented for assessing the epidemiological value of BCG and its public health indications, can help appreciate the advantages and disadvantages brought by vaccination in high- as well as in low-prevalence countries. The article focuses on the future, i.e. on what can, from now on, be expected from BCG in terms of epidemiological, economical and psychological benefits. Test runs were made considering three cohorts of 100,000 individuals (newborn, school enterers, school leavers), vaccinated or not vaccinated, submitted to various risks of infection (corresponding to conditions of high-, intermediate- and low-prevalence of tuberculosis) and experiencing various breakdown rates from infection to disease. Cost for BCG on the one hand, and cost for diagnosis, treatment of tuberculosis and loss of wages on the other, were also entered in the calculations; an attempt was also made to quantify in absolute terms and in relative ones the in conveniences linked to the application of BCG itself. Beyond figures and results presented as examples, what is more important is that the article furnished a method of reasoning and the possibility to feed one's own data in the model; it may help to encompass the scope and implications of a decision, and it furnishes elements of dialogue with other members of the planning team. It should be well realized that the elements provided and those which can be worked out are elements of reflexion to found a decision; the decision itself - to start, to pursue or to stop BCG on a mass scale - is of political nature (public health policy): it always implies a value judgement - from the part of the providers of the services and/or, preferably, from the part of the users, i.e. a preference which is the result of a 'weighing' between advantages and inevitable disadvantages, both involving time, place, existing system, existing beliefs and other fields of health and welfare.