HIV Prevention Cost per DALY vs. percent GDP per capita (Africa). Notes/Sources: The graph plots the studies reviewed in terms of US$ cost per DALY and the same US$/DALY as percent of country-specific per-capita gross domestic product (GDP) taken from the International Monetary Fund, World Economic Outlook Database . US$/DALY is the cost per disability-adjusted life year, DALY (US dollars, year of costing as reported in each study, log transformed). When cost/DALY was not available in the studies, we assumed it was equal to the cost per infection averted/20 for adults, 25 for children [3, 18]; one study used cost per QALY . For details of each study, see Additional File 1.