'25 at 25': PROUD - preventing HIV infections

02 Dec 2024

In 2015 results were released from the PROUD study showing a daily pill could play a major role in reducing the number of new HIV infections among men who have sex with men. We look back on the remarkable success of this study, as part of our ’25 at 25’ series celebrating the MRC Clinical Trials Unit’s 25^th anniversary.

PROUD was the first study of the pre-exposure prophylaxis approach to preventing HIV to be carried out in the UK. 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 in addition to standard prevention was an effective way to prevent HIV infection. The results show that PrEP is highly protective, reducing the risk of infection for this group by 86%. They also revealed that the risk of acquiring HIV was very high in a sub-population of men who have sex with men.

A total of 544 people from 13 sexual health clinics in England took part in the study; community organisations played a crucial supporting role. They were men and transgender women 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 the offer of 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.

Only three men in the immediate PrEP group were infected with HIV, compared to 20 in the group who did not receive PrEP immediately. The three men who were infected in the immediate PrEP group were unlikely to have actually been taking PrEP when they were infected - one was probably infected before he started PrEP, and the other two had not collected their prescription of PrEP for several months before being diagnosed.

The drug used in the trial - the antiretroviral Truvada (a drug 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 how good Truvada would be found as PrEP in a real world situation where participants knew that they were taking an active drug instead of the possibility of it being a placebo. 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.

PROUD found no difference in the number of men diagnosed with other STIs between those on PrEP and those not on PrEP.

For more information about the PROUD study, watch the documentary which contains interviews with researchers, doctors, study participants and community groups.

The British HIV Association published new PrEP guidance in 2015 with PROUD findings embedded throughout as key evidence to help clinicians support individuals who decided to purchase the drug for themselves. The US Centers for Disease Control and World Health Organization (WHO) guidance followed suit, also citing PROUD.

In the UK, the success of PROUD led many individuals to self-purchase the drug, but the NHS was cautious of commissioning the drug in spite of the evidence for cost-effectiveness. This was because the demand, and therefore the overall budget, was not clear. To determine this, they funded the PrEP Impact Trial, which the MRC CTU at UCL played a key role in supporting. 26,000 people took part in the study, which looked at how many people attending sexual health clinics need PrEP, how many start PrEP, and how long they need it for. Interestingly the study found the same level of effectiveness in reducing HIV infections as PROUD. This, together with the PROUD results, led to PrEP becoming available through the NHS.

The widespread uptake of PrEP among people at risk of HIV has contributed to a decline in new HIV infections in the UK.

Further information