B.c.g. Tuberculin By

It is well known that after Bacille Calmette-Gue'rin (B.C.G.) vaccination the degree of allergy as shown by the tuberculin test is of a lesser order than that after infection with virulent tubercle bacilli. For this reason it may be necessary to perform several successively stronger tuberculin tests up to 100 units of old tuberculin (Mantoux 1/100) before a positive post-vaccination test is obtained. Several tests, however, are inconvenient to patients and physicians alike. In addition, a test with 100 tuberculin units may well give rise to non-specific false positive reactions. Several investigators abroad have reported that a tuberculin prepared from the B.C.G. substrain of tubercle bacilli is a more sensitive indicator of tuberculin allergy in vaccinated persons (Bluhm, 1949; Hagberg, 1950; Lind and Holm, 1943; Magnusson, Lithander and Hagberg, 1949; Ruziczka, 1952a and b; Quaiser, 1954). As we required a sensitive quantitative test to evaluate the antigenic properties of several batches of newly introduced freeze-dried B.C.G. vaccines of British manufacture (Lorber, Hart, Farmer and Muggleton, 1956; Lorber, Farmer and Muggleton, 1957), we decided to conduct a controlled trial of B.C.G. tuberculin as one of the post-vaccination tests.