Scientists gave the pill, which is currently used to treat people who have contracted the virus, to healthy gay and bisexual men during the three-year global trial.
They discovered daily doses of the pill, Gilead Science’s Truvada, cut the risk of infection when given with condoms, counselling and other prevention services.
The drug lowered the chances of infection by 44 per cent, and by 73 per cent or more among men who took their pills most faithfully.
Researchers had feared the pills might give a false sense of security and make men less likely to use condoms or to limit their partners, but the opposite happened – risky sex declined.
The results are ‘a major advance’ that can help curb the epidemic in gay men, said Dr. Kevin Fenton, AIDS prevention chief at the U.S. Centers for Disease Control and Prevention.
But he warned they may not apply to people exposed to HIV through male-female sex, drug use or other ways. Studies in those groups are under way.
Because Truvada is already on the market, the CDC is rushing to develop guidelines for doctors who want to use it to prevent HIV, and urged people to wait until those are ready.
However, high prices of the pills which cost US$5,000 to US$14,000 a year in the United States could be prohibitive.
They are sold for roughly US$140 a year in some poor countries where they are produced in generic form.
Whether insurers or government health programmes should pay for them is one of the tough issues to be sorted out, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
‘This is an exciting finding,’ but it ‘is only one study in one specific study population,’ so its impact on others is unknown, Fauci said.
His institute sponsored the study with the Bill & Melinda Gates Foundation.
It was the second piece of good news in a day for the fight against AIDS after U.N. officials said new HIV cases are dropping dramatically worldwide.
The U.N. report said that new cases dropped nearly 20 percent over the last decade and that 33.3 million people are living with HIV now.
And earlier, the Pope, in a shift from historic teachings, said that using a condom is a lesser evil than infecting a sexual partner with HIV.
Gilead Sciences Inc. donated Truvada for the study, which involved about 2,500 men at high risk of HIV infection in Peru, Ecuador, Brazil, South Africa, Thailand and the United States.
The foreign sites were chosen because of high rates of HIV infection and diverse populations.
More than 40 per cent of participants had taken money for sex at least once. At the start of the study, they had 18 partners on average; that dropped to around six by the end.
The men were given either Truvada or dummy pills. All had monthly visits to get HIV testing, more pills and counselling.
Every six months, they were tested for other sexually spread diseases and treated as needed.
After a median follow-up of just over a year, there were 64 HIV infections among the 1,248 men on dummy pills, and only 36 among the 1,251 on Truvada.
Among men who took their pills at least half the time, the risk of infection fell by 50 per cent. For those who took pills on 90 per cent or more days, risk fell 73 per cent.
Tests of drug levels in the blood confirmed that more consistent pill-taking gave better protection, and in one subgroup, the reduction in risk was 92 per cent.Post published in: News