1. Merck and Co. Inc., PO Box 4 WP 26–265, Sumneytown Pike, West Point, PA 19486, USA 2Merck and Co. Inc., PO Box 2000 RY80Y 230, 126 E. Lincoln Ave., Rahway, NJ 07065, USA 3PHRI TB Center, Public Health Research Institute, 225 Warren Street, Newark, NJ 07103, USA