Contact tracing of tuberculosis in a school setting and the relevance of BCG in this population.

Tuberculosis (TB) remains a worldwide health problem. Treatment, contact tracing and screening of at-risk populations continue to be important issues even in countries with low rates of tuberculosis. In contact tracing, prior BCG vaccination can make interpretation of Mantoux positivity difficult. We had the opportunity to evaluate contacts of a student diagnosed with pulmonary tuberculosis. In the index case's class, 23 of 50 (46%) students screened had TB infection and a further 2 (4%) students had TB disease. Screening was offered to all students in the school (307 students) and 244 students (79%) attended. Students were stratified naturally into classes of ascending age, providing an opportunity to study disease transmission and Mantoux testing in a group who had received BCG at birth. Our findings illustrates that neonatal BCG vaccination has a minimal effect on Mantoux positivity at 12 years and older.