The present position of B.C.G. vaccination.

It is now generally recognized that a primary tuberculous infection evokes a definite degree of acquired resistance to reinfection. This primary infection, though usually innocuous to the European, may produce progressive disease. For the last seventy years research has been directed towards finding a vaccine that will produce an avirulent primary infection and evoke acquired resistance in safety; from this has emerged tke B.C.G. vaccine and, more recently, the Vole vaccine. The history of B.C.G. up to 1948 has been dealt with in detail elsewhere (Irvine, 1949); this article is primarily concerned with advances which have occurred since then and with its recent introduction into this country.