Should doctors prescribe to healthy people engaged in high-risk behavior an $11,000-a-year drug that is not as effective as condoms in preventing HIV infection?

That question about approaches to prevention created some of the most heated debate at the 19th International AIDS Conference in Washington this week.

When opponents argued that such a drug will give users a false sense of security that would discourage condom use, scientist Linda-Gail Bekker retorted: “Do people think that if we give people more statins (drugs to lower cholesterol), they will eat more ice cream? Why don’t we ever ask that?”

Concerns were also raised about allocation of resources and the danger of creating resistance to drugs invaluable in treating those already infected.

The debate was inspired by a prevention tool called pre-exposure prophylaxis, or PrEP, which involves giving anti-retroviral drugs to HIV-negative people who are at high risk of infection. The drug is envisioned as part of “combination prevention” that would include, for example, condoms and circumcision.

On July 16, the Food and Drug Administration approved the first drug for PrEP in the United States — an oral, once-a-day pill called Truvada. The drug, marketed by Gilead Sciences, is for healthy, high-risk individuals, such as men who have sex with men and partners of HIV-positive people.

The first trial demonstrated a 39 percent decrease in risk of contracting HIV for at-risk women in South Africa who were given Truvada in the form of a vaginal microbicide. Later that year, another study showed that gay men who took a daily pill of Truvada reduced their risk of infection by 44 percent. Two more trials involving heterosexual men and women in southern Africa showed an efficacy of up to 75 percent.

By comparison, circumcision is about 60 percent effective in preventing HIV infection. Next to abstinence, condom use is the most effective preventative — 90 to 95 percent if used consistently.

In addition to concerns about discouraging condom use, opponents raise ethical issues about cost. Fewer than 50 percent of people globally with HIV are receiving the treatment they need, according to the United Nations Program on HIV/AIDS. Moreover, many other diseases and illnesses are rampant, including those that are inexpensive to prevent or treat.

Truvada is estimated to cost about $11,000 annually per person, and generic versions of the therapy will not be available until Gilead Sciences’s patent expires in 2021.

Harvard researcher Douglas Krakower, who also presented his work Wednesday, analyzed how Truvada is perceived by those who may be most likely to use it now — namely, men who have sex with men in North America.

He surveyed about 5,000 such men recruited through an online dating site. Seventy-five percent reported interest in using Truvada or any similar drug that might be approved. However, 20 percent anticipated they would decrease condom use if they did take such a pill.

Nelly Mugo, a leading HIV-prevention expert at the Kenyatta National Referral Hospital, said PrEP could be an empowering tool for vulnerable populations, for example people living in places where rape is used as an instrument of war. She also envisions PrEP being “taken for a season” — a short period of high risk, such as when couples with one HIV-positive partner are trying to conceive a child, when intimate-partner violence or sex work is involved, or when depression or substance abuse is a factor discouraging condom use.

Mugo notes that the tactic is unusual in that it gives women a prevention tool that they can control.

Krakower and other scientists urged after presenting their work that the full benefits of PrEP can only be achieved if physicians are trained to prescribe and monitor its use responsibly as part of a “prevention package” that includes condom use and behavioral counseling.

Krakower added that consistent HIV testing would have to be carried out for those on PrEP to ensure that they would not unknowingly acquire HIV infection while taking anti-retrovirals — a dangerous opportunity for their viral strains to gain resistance to drugs.

Mugo proposed that patients be provided newly approved “HIV home testing kits” that could be coordinated with renewals of PrEP prescriptions.

Heated discussion after presentation sessions made clear that physicians remain divided about prescribing Truvada or other PrEP drugs that are in the pipeline. One doctor, referring to the fact that condoms are cheaper and more effective, shouted angrily to Krakower, “How is this not a violation of the Hippocratic oath?”

Krakower disagreed. “I think it’s a violation of the oath to withhold strategies that may be protective,” he said.

He adding that PrEP development is a young and rapidly evolving field.

“If later evidence says [prescribing PrEP isn’t a good idea], I think it’s within the Hippocratic oath to change my mind. We must always let the evidence guide what we do,” he said.