[1] London Sch Hyg & Trop Med, Dept Global Hlth & Dev, London WC1, England
[2] Minist Hlth, Hlth Intervent & Technol Assessment Program, Bangkok, Thailand
[3] Bill & Melinda Gates Fdn, Seattle, WA USA
[4] Univ Cape Town, Sch Publ Hlth & Family Med, Hlth Econ Unit, ZA-7925 Cape Town, South Africa