Ten year evaluation of a trial of chemoprophylaxis against tuberculosis in Frobisher Bay, Canada.

A trial of chemoprophylaxis to prevent tuberculosis in Canadian Inuit (Eskimos) was carried out in Frobisher Bay, Canada during 1971-1974. A completely supervised regimen of isoniazid and ethambutol thrice weekly for 18 months was administered. A 10-year evaluation of 370 treated persons and 217 control subjects demonstrates the sustained value of adequate chemoprophylaxis in reducing the risk of developing active tuberculosis in the 3 groups under study--1, those with a previous episode of active tuberculosis, 2, positive tuberculin reactors with normal chest X-ray and 3, BCG vaccinated individuals with large tuberculin reactions. There were 3 cases of active disease in the treated group, a risk of 0.1% per annum, and 13 cases among the controls, a risk of 1.0% per annum.