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PROUD study shows Pre-Exposure Prophylaxis is highly protective against HIV infection

25 February 2015

Researchers from the MRC CTU and Public Health England have presented results at a conference in Seattle, Washington, indicating that pre-exposure prophylaxis reduces the risk of HIV infection by 86% for gay and other men who have sex with men in England.

Pre-exposure prophylaxis (PrEP) is a HIV prevention strategy that involves HIV-negative people taking antiretroviral drugs to reduce the risk of becoming infected if they are exposed to the virus. The PROUD study  looked at whether offering daily PrEP to men who have sex with men was an effective way to prevent HIV infection.  The results released at the Conference on Retroviruses and Opportunistic Infections yesterday indicate that PrEP is highly protective for this group, reducing the risk of infection by 86%. The researchers concluded that PrEP offers a major opportunity to curb new HIV infections in men who have sex with men in the UK.

The drug used in the trial - the antiretroviral Truvada (usually used to treat HIV) - was already known to reduce the incidence of HIV infection in placebo  controlled trials.  The PROUD study was designed to see if the same effect would be found in a real world situation where participants knew they were taking an active drug.  It aimed to address outstanding questions such as whether taking PrEP would change sexual risk behaviour - for example increasing the number of partners they did not use condoms with and increasing the rate of other sexually transmitted infections (STIs) - and whether or not it would be cost-effective to make it available on the NHS. 

The study was launched in 2012, enrolling 545 participants at 13 sexual health clinics in England. The study enrolled men who have sex with men, who reported having had anal sex without a condom in the previous 3 months. The study randomised participants to receive PrEP immediately or to receive PrEP after a period of 12 months, allowing researchers to compare those on PrEP versus those not yet on PrEP.  There were 1.3 new infections per 100 person-years in the group given PrEP immediately, and 8.9 per 100 person-years in the group who were not yet on PrEP. The 86% protection from daily PrEP reported by the study is the highest reported from any randomised controlled trial of PrEP to date.

The sexual health research clinics that took part in the PROUD study were able to integrate PrEP into their routine HIV risk reduction package.  Participants incorporated PrEP into existing risk reduction strategies, which included condom use.  There was no difference in the number of men diagnosed with other STIs between those on PrEP and those not on PrEP.

Sheena McCormack, Professor of Clinical Epidemiology at the MRC Clinical Trials Unit at UCL, and Chief Investigator of the PROUD study, said: "These results are extremely exciting and show PrEP is highly effective at preventing HIV infection in the real world. Concerns that PrEP would not work so well in the real world were unfounded. These results show there is a need for PrEP, and offer hope of reversing the epidemic among men who have sex with men in this country. The findings we've presented today are going to be invaluable in informing discussions about making PrEP available through the NHS."

The PROUD study was led by the MRC CTU at UCL and Public Health England in partnership with 12 NHS trusts in England.