Stanford medical student Nathan Lo reportedly caused a stir at the Conference on Retroviruses and Opportunistic Infections (CROI) last week when he presented a new finding: After analyzing surveys completed by 800,000 people in 22 sub-Saharan African countries, Lo and his colleagues found “no evidence to suggest that PEPFAR funding of abstinence and faithfulness programs results in reduced high-risk sexual behavior.”

Using data from the US-funded Demographic and Health Survey, the Stanford researchers analyzed responses to questions about the number of sexual partners, age of first sexual experience, and teen pregnancy. They then compared trends in 14 PEPFAR-funded and eight non-PEPFAR-funded countries, and found no evidence to suggest PEPFAR abstinence and faithfulness programs were associated with significant reductions in numbers of sexual partners, lower age of first sexual experiences, or fewer teen pregnancies. The New York Times’ Donald G. McNeil Jr. reports on the audience’s response to Lo’s presentation:

Global health specialists came to the microphone to congratulate Mr. Lo. Advocates who had long opposed the American policy that sought to prevent AIDS by promoting abstinence and faithfulness applauded.

“That was fantastic,” said Dr. Gilles van Cutsem, medical coordinator for Doctors Without Borders in South Africa.

Staff members from the government program that Mr. Lo had accused of wasting money — Pepfar, the President’s Emergency Plan for AIDS Relief — came up afterward to quietly congratulate him. When they realized a reporter was present, they nervously asked that they not be named.

President George W. Bush’s global AIDS plan was enacted in 2003 and marshaled billions of dollars to treat Africans who had AIDS with lifesaving drugs. Conservative Republican leaders in the House of Representatives successfully included a provision that one-third of AIDS prevention money go to programs to encourage abstinence and fidelity. That campaign — known as ABC, for abstain, be faithful and use condoms — was part of the bargain made when Christian conservatives joined with liberals to pass the law.

Keith Alcorn reports at AIDSmap that abstinence funding accounts for a smaller portion of PEPFAR money than it used to:

In 2008, the legislative requirement changed: since then, programmes have been required to justify to Congress why they spend less than 50% of prevention funding on these programmes.

Funding for the programmes peaked at $200 million a year in 2008, but declined to around $50 million in 2013, as money has been directed to other measures with stronger evidence of effectiveness.

Programmes aimed to delay sexual debut in order to reduce the period of high risk during adolescence, especially for girls, and to reduce partner numbers. Although there may be epidemiological grounds for thinking that delaying sexual debut and reducing sexual activity might reduce opportunities for acquiring HIV, evidence for effective interventions was lacking when Congress earmarked funding.

PEPFAR has done a lot of good. If health advocates faced a choice between no global AIDS program and a global AIDS program with one-third of funding going to abstinence, supporting the compromise was the right choice. Changing funding priorities based on emerging evidence of effectiveness (or non-effectiveness) is something government-funded programs should do. Ideally, the legislation creating new public-health interventions will always contain requirements and funding for studying programs’ effectiveness, as well as mechanisms for altering programs in response to new evidence. We shouldn’t let the perfect be the enemy of the good, but we should also work quickly to perfect good programs.