 At each study encounter, possible toxicity will be assessed via interview. Patients will be followed every 6 months after the completion of preventive therapy until the study closes. Outreach workers will perform home visits to encourage follow-up and determine vital status for any patient who has missed a scheduled follow-up visit. Patients with evidence of active tuberculosis at any follow-up visit will be evaluated and treated appropriately. Patients will be offered a small incentive for fulfilling study requirements. The equivalent of 5 30 rand will be paid after successful entry into the trial and at each 6 month visit as compensation for time spent in the study and to cover travel expenses. 