FOSTER CITY, Calif. – Scientists believe they have found a pill that can help healthy gay men stay HIV-negative.

A recent study of HIV-negative men who took a daily dose

of the HIV medication Truvada, were able to cut their risk of HIV infection by 44 percent when given with condoms, counseling and other prevention services. Men who took their pills most faithfully had even more protection, up to 73 percent. About 20,000 people were involved in the study.

Scientists are worried that those who are prescribed the pill will engage in more risky sexual behavior, because they believe they are better protected against contracting HIV.

The pills cost from $5,000 to $14,000 a year in the United States, but only 39 cents a day in some poor countries where they are sold in generic form.

“It’s not time for gay and bisexual men to throw out their condoms,” said Dr. Kevin Fenton, AIDS prevention chief at the CDC. “The pill should never be seen as a first line of defense against HIV.”