ATLANTA -- Scientists have long believed that a vaccine is the best way to stop the spread of AIDS, but efforts to invent one have miserably flopped.

It's a combination of two drugs that have shown such promise in early experiments in monkeys that officials just expanded tests of them in people around the world.

"This is the first thing I've seen at this point that I think really could have a prevention impact," said Thomas Folks, a federal scientist since the earliest days of AIDS. "If it works, it could be distributed quickly and could blunt the epidemic."

Condoms and counseling alone have not been enough -- HIV spreads to 10 people every minute, 5 million every year. A vaccine remains the best hope but none is in sight.

If larger tests show the drugs work, they could be given to people at highest risk of HIV -- from gay men in American cities to women in Africa who catch the virus from their partners.

"I've had people make comments to me, 'Aren't you just making the world safer for unsafe sex?'" said Dr. Lynn Paxton, team leader for the project at the Centers for Disease Control and Prevention.

The drugs would only be given to people along with counseling and condoms, and regular testing to make sure they haven't become infected. Health officials also think the strategy has potential for more people than just gay men, though they don't intend to give it "to housewives in Peoria," as Paxton puts it.

Some uninfected gay men already are getting the drugs from friends with AIDS or doctors willing to prescribe them to patients who admit not using condoms. This kind of use could lead to drug resistance and is one reason officials are rushing to expand studies.

"We need information about whether this approach is safe and effective" before recommending it, said Dr. Susan Buchbinder, who leads one study in San Francisco.

Taking them daily or weekly before exposure to the virus -- the time frame isn't known yet -- may keep it from taking hold, just as taking malaria drugs in advance can prevent that disease when someone is bitten by an infected mosquito, scientists believe.

Specifically, six macaques were given the drugs and then challenged with a deadly combination of monkey and human AIDS viruses, administered in rectal doses to imitate how the germ spreads in gay men.

Despite 14 weekly blasts of the virus, none of the monkeys became infected. All but one of another group of monkeys that didn't get the drugs did, typically after two exposures.

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