Yes, you can use pills to prevent AIDS, review finds Drugs used to control the AIDS virus can also be used to protect uninfected people, researchers concluded on Tuesday in a "last-word" review of the data. Their report, released in the Cochrane Library, bolsters calls for policies backing distribution of the drugs to people most at risk from the virus -- including gay and bisexual men, drug users, and women in some African-American communities as well as across the developing world. The findings also underscore the debate over how best to use scarce resources to fight the pandemic of human immunodeficiency virus or HIV, which infects 33 million people globally, including more than a million in the United States. It has killed 25 million people. There is no cure and no vaccine. But studies are showing hope on several fronts. "We think we are at the beginning of the end of the AIDS epidemic," Dr. Diane Havlir, an AIDS specialist at the University of California, San Francisco, and one of the organizers of a giant, international AIDS conference being held in Washington, D.C. later this month, told reporters on Tuesday. Over the past three years, there has been a series of breakthroughs in interventions that can dramatically curb the rate of infections with HIV. Work on a vaccine is promising, it's been shown clearly that circumcising men protects them from infection, and it's also obvious that treating infected people not only keeps them alive and healthy, but it helps prevent them from infecting others. Work is also progressing on a microbicide -- a gel that women could use to protect themselves from infected husbands and partners. And now research is also showing that giving people a once-a-day dose of the pills used to treat HIV can keep them from becoming infected in the first place. The studies on this last approach, called pre-exposure prophylaxis or PrEP, have been mixed. So Charles Okwundu of Stellenbosch University in South Africa and colleagues studied the studies. They looked at experiments involving more than 9,800 people around the world at high risk of becoming infected with HIV, including gay or bisexual men and sex workers. The drug tenofovir alone -- sold under the brand name Truvada by Gilead Sciences -- cut the risk of HIV infection by nearly two-thirds, while trials using Truvada with a second drug called emtricitabine, brand name Emtriva, cut the risk by 49 percent, they reported in the Cochrane Library, a journal that seeks to find the "last word" on studies. It's not clear why using two drugs seemed to be less effective than using just one, but the trials were done very differently and using different groups of people. "Our findings suggest that antiretroviral drugs can reduce the risk of HIV infection for people in high risk groups," Okwundu said in a statement. However, in the search for highly reliable HIV prevention strategies, it is important to determine how pre-exposure prophylaxis can best be combined with existing programs, as no strategy is likely to be 100 percent effective. Okwundu's team noted controversy over using PrEP. "One concern is the long-term side effects of antiretroviral drugs used over many years by uninfected individuals," they noted. These include possible kidney damage and bone loss. In addition, if people don't take the drugs consistently, they could develop what is known as resistant virus -- infections that defy the use of drugs. This can hurt the patients themselves, and they can also pass this resistant and hard-to-treat virus to others. "There also are concerns that PrEP will lead to an increase in high-risk behavior," Okwundu's team adds. If PrEP is not completely effective, even a partial reduction in use of safer sex could lead to an increased rate of HIV transmission. And the drugs are expensive -- Truvada costs more than $1,000 a month in the United States, although Gilead allows for much cheaper generic versions to be made and distributed in the developing world. Despite the concerns, in May a panel of Food and Drug Administration advisers recommended that the FDA approve the pills for this use. Already, doctors can and often do prescribe the pills as they like, but FDA approval would clear the way for U.S. insurance companies to pay for it and for the company to promote the drug for this use. Related stories on Vitals: Melissa Harris-Perry sat down with former House Speaker Nancy Pelosi on Friday to discuss - among many issues - the congresswoman's work in combating the HIV crisis. Christopher MacDonald Dennis, dean of multicultural life at Macalester College, joins Harris-Perry to talk about what HIV and AIDS looks like in America today.