The U.S. President's Emergency Plan for AIDS Relief (PEPFAR) has saved at least a million lives in sub-Saharan Africa but does not appear to have curbed the epidemic, a new study suggests.

"PEPFAR has been on the whole an extremely successful program," says study co-author Eran Bendavid, an infectious disease and health policy researcher at Stanford University in Palo Alto, Calif. But, he says it's unclear how successful it was at preventing new cases of HIV. 

In May 2003, President George W. Bush signed legislation authorizing PEPFAR, a commitment by the U.S. to spend $15 billion over five years to prevent HIV/AIDS and treat victims in Africa, Asia, and the Caribbean -- "the largest commitment by any nation to combat a single disease in history," according to the program's official Web site.

To find out how PEPFAR has impacted the HIV/AIDS epidemic, Bendavid and his colleague Jay Bhattacharya, an associate professor of medicine at Stanford, analyzed HIV statistics from the five years before PEPFAR's launch (1997-2002) and the four years after (2004–2007), comparing 12 African countries that had received PEPFAR assistance with 29 that had not.

Their findings, published in The Annals of Internal Medicine: that the program put a big dent in the number of deaths from the disease but not in the number of people who are living with it.

"We found that in the years when PEPFAR was operating in focus countries, the number of deaths [from HIV/AIDS] was about 10 percent lower than what we would expect based on historical information and what was happening in other countries [translating to about a million lives saved over four years],” Bendavid says. But "we do not see any appreciable change in prevalence."

He says it's a mystery why the number of cases didn't decline. He speculates that perhaps four years was not enough time for the program to make inroads. Or the increased availability of antiretroviral drugs may have emboldened people to engage in more risky sexual behaviors (as seen in the 1990s, when the introduction of antiretroviral drugs in homosexual men in the U.S. led to more risky behavior), Bhattacharya notes.

In an attempt to figure out why PEPFAR failed to stem the HIV epidemic, Bendavid and Bhattacharya have launched a study examining whether falling prices for antiretrovirals encourages people to practice risky sex. 

In 2008, Bush reauthorized PEPFAR for another five years, this time tripling the U.S. commitment to as much as $48 billion.

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