Full Length ReportStudies in the Allergy of Infection: I. Responses of the Skin to BCG Vaccination in Various Categories of Tuberculin Sensitivity*

introduction When a large, unselected and statistically valid number of modern city dwellers is tested by intracutaneous injection of tuberculin in the usual test dose of about 7 of a milligram of Old Tuberculin Koch (0.1 cm. of a dilution of 1:5,000 OTK), some will react and some will not. If such testing is done nowadays on large groups distinguished by ages, the results are likely to be approximately as follows: Between birth and 2 years (in infancy), almost all will fail to react. Between 2 and 10 years, many fewer will react than not. Between 10 and 20 years, reactors and non-reactors will be nearly equal in number.