1. a Applied Research Department , Family Health International , PO Box 13950, Research Triangle Park , NC , 27709 , USA
2. b East, Central and Southern African Health Community , Arusha , Tanzania
3. c School of Nursing , Muhimbili University of Health and Allied Sciences , Dar es Salaam , Tanzania
4. d Behavioral and Biomedical Research , Family Health International , Research Triangle Park , NC , USA