PrEP prevents HIV spread in gay men, finds study

An anti-viral drug has been found to prevent HIV infection in hundreds of healthy gay men, scientists have revealed.

The daily pre-exposure prophylaxis (PrEP) treatment stopped transmission of the virus in the high-risk group.

Scientists at the Kaiser Permanente San Francisco Medical Center said their study marks the first and largest published evaluation of the drug in a clinical setting.

Over the course of 32 months researchers examined 657 people who were started on a PrEP treatment plan. And not one of them developed HIV during the course of the study.

Previous clinical trials of the drug suggested it had a prevention rate of about 86 per cent, not 100 per cent as the current study does. 

Critics of the drug say the daily pill encourages risky sexual behaviour among gay and bisexual men. But proponents say it has the potential to slash the number of HIV cases if given as a preventative method across the world.

The average length of use of the drug was 7.2 months, giving the team 388 person-years of observation to analyse.

The average age of PrEP users in the study was 37, and 99 per cent were men who have sex with men.

In 2012, the US Food and Drug Administration (FDA) approved a fixed-dose treatment of emtricitabine and tenofovir - known commercially as Truvada - for people who do not have HIV but are at high risk of contracting the virus.

The drug was approved for daily use in combination with safer sex practices, as a means of preventing HIV.

When someone is exposed to HIV through sexual activity or injection drug use, Truvada can keep the infection from becoming permanent.

Dr Jonathan Volk, physician and epidemiologist at Kaiser Permanente San Francisco Medical Center said: ''Our study is the first to extend the understanding of the use of PrEP in a real-world setting and suggests that the treatment may prevent new HIV infections even in a high-risk setting.

''Until now, evidence supporting the efficacy of PrEP to prevent HIV infection had come from clinical trials and a demonstration project.''

His team found that compared with people who did not use the PrEP protocol, users were more likely to report multiple sex partners, but were not more likely to report having an HIV-infected sexual partner.

Of 143 patients who were asked about behaviour change after six months of PrEP use, the number of sexual partners was unchanged for 74 per cent, decreased for 15 per cent and increased for 11 per cent of participants.

Condom use was unchanged in 56 per cent, decreased in 41 per cent, and increased in 3 per cent.

At six months after initiation, 30 per cent of PrEP users had been diagnosed with at least one sexually transmitted infection, or STI.

At 12 months, 50 per cent of PrEP users had been diagnosed with any STI; 33 per cent had a rectal STI, 33 per cent had chlamydia, 28 per cent had gonorrhea, and 5.5 per cent had syphilis.

Dr Julia Marcus, co-author of the study, said, ''Without a control group, we don't know if these STI rates were higher than what we would have seen without PrEP.

''Ongoing screening and treatments for STIs, including hepatitis C, are an essential component of a PrEP treatment programme.''

The study was published today in the journal Clinical Infectious Diseases.

It comes after the PROUD study, published earlier this year and conducted at University College London, found that preventative use of PrEP was effective, prompting experts to advise the drugs are made available on the NHS.

Shaun Griffin, executive director of external affairs at the Terrence Higgins Trust, said, 'These are really exciting findings that demonstrate the effectiveness of PrEP in a group of men who have an increased likelihood of acquiring HIV.

''Results already published from the PROUD study showed there was essentially no difference in the levels of STIs amongst the two groups of men at increased likelihood of acquiring HIV, one of which was treated with the PrEP drug Truvada immediately, and the other group deferred starting treatment for a year.

''We now await the publication of these results of the UK-based PROUD trial in a peer review journal.

''This will be an important marker in making the case for PrEP availability on the NHS. We expect this publication very soon.''