It’s no morning-after pill. But while the jury’s still out about post-exposure prophylaxis, or PEP—a monthlong HAART regimen that, if started within 72 hours of exposure to HIV, may prevent infection—the trend is up. In May, New York’s Beth Israel Medical Center began to offer PEP to the public, despite efficacy, safety and other doubts.

“We believe it’s safe,” said Jeffrey Martin, MD, at the University of California San Francisco’s Center for AIDS Prevention Studies (CAPS). “We’re not certain it works. We know there’s no alternative. Given that information, I think it should be offered.”

Once reserved for health care workers who feared needle-stick infections—PEP works in four out of five—the pills have been increasingly available since the first pilot programs sprang up in 1997. New data have helped retire fears about PEP and sexual transmission. In a 400-person study, CAPS found that people will seek PEP after unsafe sex if they know it is available, and that PEP does not encourage an increase in unsafe sex—only 12 percent were repeat visitors. Moreover, 78 percent finished the full month of treatment (a much higher rate than among health care workers). About a third reported side effects, which went away upon completion. They also found that people will return for follow-up testing and counseling. Best of all, none of the 400 CAPSers tested positive, though Martin said that’s not proof that PEP works. Given that the chances of infection from a single sexual exposure to HIV is 1 in 100 to 200, it’s unclear how many people would have seroconverted even without PEP. But a PEP study at Boston’s Fenway Community Health Center has shown similar results to those from CAPS.

As evidence in favor of PEP mounts, attitudes seem to be shifting. Even AIDS prevention experts concerned about PEP encouraging unsafe sex have begun to cool their heads. “There’s nothing in my mind that says, ‘Oh God! People shouldn’t know about PEP because then they’ll go have sex without condoms!’” said Thomas Dunning, HIV prevention manager at Chicago’s Howard Brown Health Center. Still, one leading AIDS organization said privately, “PEP is the last thing we really want people to know about.”

Since May, PEP experts have lobbied the Centers for Disease Control and Prevention to change its guidelines to include treatment for those exposed sexually. While a CDC rep said the agency does not expect to change its recommendations “anytime soon,” backers Martin and Boswell predict a policy reform by next spring.