PrEP should be offered urgently to gay men with a recent STI or multiple condomless partners

Analysis of men who acquired HIV in the deferred arm of the PROUD study highlights two risk factors that are far more important than any others. “A recent history of syphilis or rectal chlamydia/gonorrhoea, or multiple ncRAI [receptive anal intercourse without a condom] partners indicates a high imminent risk of HIV infection,” Ellen White of University College London and colleagues write in Sexually Transmitted Infections. “MSM [men who have sex with men] with any of these characteristics should be offered PrEP [pre-exposure prophylaxis] as a matter of urgency.”

The analysis is based on the 268 participants who took part in PROUD, the study of PrEP in England, and were randomly allocated to the deferred arm (those who did not initially receive PrEP).

Participants’ median age was 35; 40% were born outside the UK and 70% were recruited at a London clinic. In the previous year, 40% had been diagnosed with rectal chlamydia, rectal gonorrhoea or syphilis. There was a wide range of numbers of sexual partners between participants, with half having more than ten partners in the previous three months. This was a cohort at unusually high risk of HIV, who are not representative of the wider population of gay men in England, but do reflect a group who were motivated to take PrEP.



The last part of the large intestine just above the anus.


A sexually transmitted infection caused by the bacterium Treponema pallidum. Transmission can occur by direct contact with a syphilis sore during vaginal, anal, or oral sex. Sores may be found around the penis, vagina, or anus, or in the rectum, on the lips, or in the mouth, but syphilis is often asymptomatic. It can spread from an infected mother to her unborn baby.


Chlamydia is a common sexually transmitted infection, caused by bacteria called Chlamydia trachomatis. Women can get chlamydia in the cervix, rectum, or throat. Men can get chlamydia in the urethra (inside the penis), rectum, or throat. Chlamydia is treated with antibiotics.

post-exposure prophylaxis (PEP)

A month-long course of antiretroviral medicines taken after exposure or possible exposure to HIV, to reduce the risk of acquiring HIV.


Receptive anal intercourse refers to the act of being penetrated during anal intercourse. The receptive partner is the ‘bottom’.

Among those in the deferred arm, 21 individuals acquired HIV during 239 person-years of follow-up. This equates to a very high HIV incidence of 8.8%, but incidence varied according to the risk factors reported on entry to the study.

  • Incidence was 17.2% in individuals who had been diagnosed with rectal chlamydia, rectal gonorrhoea or syphilis in the previous year.
  • Incidence was 13.6% in individuals who reported having receptive anal sex, without a condom, with at least two partners in the previous three months.
  • Incidence was 1.1% in individuals with neither of these two risk factors.

Other ways of counting partner numbers (numbers of anal sex partners and numbers of receptive anal sex partners) were also associated with HIV infections, but the strongest predictor was the one mentioned above. On the other hand, there were no HIV infections in those men who reported that the only condomless sex they had was as the insertive partner (top).

There were more HIV infections in men who reported chemsex, had taken more HIV tests in the past year, had taken post-exposure prophylaxis (PEP) in the past year, and who were in full-time employment, but these did not equate to statistically significant increases in incidence.

“The results should inform eligibility criteria for MSM in the UK and similar populations elsewhere in Europe,” the authors say. All international guidelines include anal intercourse without a condom as a criterion, but generally without specifying the number of partners. Other criteria in guidelines include a recent diagnosis with a bacterial sexually transmitted infection (STI), the use of PEP and sexualised drug use.

In this study, STIs in the throat or penis were not associated with an increased HIV risk, suggesting that PrEP eligibility criteria should focus on rectal STIs and syphilis.  


White E et al. Predictive factors for HIV infection among men who have sex with men and who are seeking PrEP: a secondary analysis of the PROUD trial. Sexually Transmitted Infections, online first, 27 March 2019. (Full text freely available).