Epidemiological significance of the local reaction to direct BCG vaccination as assessed from a study in Mongolia.

Direct BCG vaccination has considerable operational advantages over the classical method of vaccinating only persons who do not react to tuberculin. In the present study it is shown that the direct method as applied in Mongolia does not cause any untoward reactions in persons who react to tuberculin and therefore can be considered a rational public health procedure.By reason of the repeated follow-up examinations, it was possible to obtain a clear picture of the development of the local BCG reactions and to test the hypothesis that these reactions may give information on pre-existing tuberculin sensitivity. It appeared impossible to deduce with any accuracy from either the local induration or the tissue destruction at the site of vaccination whether a person had tuberculin sensitivity before vaccination or not, and the results obtained with 2 different vaccines were inconsistent. It is therefore concluded that the local BCG reaction has no epidemiological significance in this respect.