Qualitative effect of BCG vaccination on sensitivity to typical and atypical tuberculins

Examination of medical student's and nursing student's sensitivity to PPD-Y, PPD-G and PPD-B before and after BCG vaccination revealed that some students who were not reactive prior to vaccination became strongly reactive to one or more of the atypical tuberculins after vaccination. This result is not due to BCG vaccine since it was not seen in guinea pigs or in children. This evidence of the interaction of multiple sensitivities after infections with different mycobacteria has significance in the interpretation of anti-tuberculosis immunity in BCG trials.