The protective effect of BCG vaccination as indicated by autopsy studies.

In a detailed study of the pathology of tuberculous infection made in Finland in 1961, tuberculous foci were found at autopsy in 61 of 67 non-vaccinated subjects and in 35 of 83 BCG-vaccinated subjects, all of whom had died between the ages of 1 and 45 years (with 2 exceptions from causes other than tuberculosis). In the present note on the same material, national information on tuberculin sensitivity and tuberculosis mortality has been used to calculate the risk of tuberculous infection in Finland at different times and ages during the lifetime of these subjects. From these risks of infection in Finland it was estimated that 63 or 64 of the non-vaccinated subjects had been infected during their lifetime and that between 25 and 31 of the BCG-vaccinated subjects were expected to have been naturally infected (had they not been vaccinated) between the time of vaccination and death. It is concluded that virtually all tuberculous infections in unvaccinated subjects lead to pulmonary foci, which are demonstrable at autopsy. Further, the same appears to be so in vaccinated subjects; there is no evidence to support the suggestion that in man BCG vaccine can prevent the establishment of infection in an exposed subject. The effects of BCG (as demonstrated in the earlier paper) appear to be confined to limiting the multiplication and dissemination of the bacilli and the development of lesions following infection.