That is the amount of money the U.S. spent over a 10-year period from 2004 through 2013 promoting abstinence before marriage as a way of preventing HIV in 14 countries in sub-Saharan Africa. Unfortunately, according to the most comprehensive independent study conducted to date of the effort, the money was more or less wasted. A rigorous comparison of national data from countries that received abstinence funding under the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) with those that got none of the funding showed no difference in the age of first sexual experience or in the number of sexual partners or teenage pregnancies—all aspects of behaviors that have been linked to a higher risk of becoming infected with HIV.

Instead the study showed that one of the most important factors associated with lower levels of risky behavior was the number of years women remained in school. Other efforts that have proved effective in slowing the spread of HIV include treating the infection in pregnant women so they do not pass the virus on to their newborns, the study added. The research by Nathan Lo, Anita Lowe and Eran Bendavid, all at the Stanford University School of Medicine, was published in the May Health Affairs.

Although the latest findings about PEPFAR's prevention efforts are disappointing, its treatment programs have been entirely more successful. A previous study by Bendavid in 2009 and another in 2012 showed that the government initiative has saved at least a million lives by making anti-HIV medications more widely available to those who need them.