Why people don’t use PEP

Awareness of PEP is not everything, as one study from Sydney presented at the 2006 Toronto International AIDS Conference found.1 Knowledge of PEP among HIV-negative gay men in Sydney had reached virtual saturation point, with 97% aware of it. However near-universal knowledge had not translated into universal use after HIV risk incidents. Just under a quarter of incidents of the very highest-risk, namely unprotected receptive anal intercourse with an HIV-positive partner, resulted in men seeking PEP.

The study was from the HIM cohort, a group of 1427 HIV-negative gay men enrolled via community venues in Sydney. Researchers conducted two interviews a year about their sexual behaviour and HIV risk factors. The yearly interviews have included asking cohort members if they knew about PEP and had ever received it.

Baseline knowledge of PEP was already high in 2001, with 79% of participants being aware of it following earlier campaigns. By 2004 this had risen to 97% of participants being aware of PEP, although this may be higher than the level of knowledge in the gay community at large, as HIM cohort members are informed and motivated enough to put themselves forward for research.

However, the question must be, why did even more men not use PEP, considering this high level of knowledge? When PEP was requested, it often followed unprotected anal intercourse with a casual partner, but PEP following sex with regular partners was less common.

In terms of the type of anal sex, 8% sought PEP when they had been the active partner in casual sex, 10% when they were the passive partner but their partner had not ejaculated inside them, but 23% when a casual partner had ejaculated inside them.

Use of PEP was not associated with any change, either positive or negative, to subsequent sexual risk behaviour with either regular or casual partners.

By the end of 2005 there had been 42 seroconversions among the HIM cohort participants, giving an overall HIV incidence of 1% a year. However, use of PEP was not associated with reduced incidence: rather the opposite. Ten men who had, at some point, sought PEP seroconverted, yielding an annual incidence among this group of 3% a year.

This does not mean that PEP, when taken, did not work, but that the men were also involved in other HIV risk incidents where they did not seek PEP. HIV incidence was higher in PEP users because risk behaviour was higher and PEP use for the occasional incident did not compensate for this fact.

Some of the reasons gay men may not use PEP after risk incidents were highlighted by another study from Toronto2 in which gay men were given ‘starter packs’ of PEP drugs. They had access to the starter packs for six months and were told to call researchers via a 24-hour helpline if they initiated PEP. They then got the remaining 25 days of PEP from their clinic. The men used their starter packs after 26% of cases of unprotected anal intercourse.

The participants in this study were gay men who were not in a monogamous relationship. The subjects were split between a youth group of 23 men aged 18 to 25 and an adult group aged 25 to 60.

Sexual risk behaviour declined in both groups during the study from two-thirds of participants reporting sexual risk behaviour at baseline to less than half at nine months.

Nearly all the adult group (89%) reported at least one episode of unprotected anal intercourse (UAI) during the study but fewer of the youth group (73%). Furthermore the men in the youth group were better at using PEP; nearly half (47%) of incidents of UAI were accompanied by PEP use in the youth group compared with only 29% of incidents in the adult group.

There was a high rate of seroconversion in the study; five men (three from the youth group and two adults) became infected during the nine months (an annual incidence of 11%). Four of the five never used PEP and the fifth did not use it during the three-month period he became infected.

So why did the men not take the pills in their bathroom cabinet after a risky episode? The poster supplies a revealing list of reasons:

  • “I just have a feeling about which partner I can trust”
  • “I’m not at risk because my partner gets tested”
  • “I’m lucky and probably won’t get HIV”
  • “I was in love with him and didn’t want to think about it”
  •  “It wasn’t risky because it was very brief”
  • “Pulling out is relatively safe”
  • “As long as my partner does not cum in me I can be certain I won’t get infected”

Since only one of the people who seroconverted said they had changed their sexual risk behaviour during the nine months, this study may document the limits of what a purely biomedical prevention intervention can do for ‘high-risk’ gay men without additional cognitive or behavioural help.

Three years later, similar findings were reported from a study of gay men in Brighton, UK.3 It suggested many were notaccessing PEP when they needed it.

The investigators conducted interviews with 15 gay men who were currently taking, or had recently completed, a course of PEP after unprotected anal intercourse. They wanted to gain a better understanding of the factors and rationale leading gay men to access PEP and how these differed from occasions which warranted PEP, but where they did not seek it.

The men generally described the risky sex that led them to seeking PEP as “rare” or a “one-off” and mentioned it within the context of drug or alcohol use. Such risk behaviour was described as being out of character; the men generally considered themselves as having a low risk of infection with HIV.

Another common theme was linking such risk behaviour with sexual partners who were in some way unusual or “other”. The men commonly attributed a number of risky characteristics to partners with whom they had had unprotected sex, such as sexually transmitted infections, promiscuity, “adventurous sex”, and a habit of having unprotected sex.

Universally, the men did not believe that they themselves had such risky characteristics.

Use of certain venues was also associated with the subsequent accessing of post-exposure prophylaxis, generally saunas, certain bars, and cruising grounds. One individual told the investigators: “It was certainly kind of one-off I think…it was in a sauna, where I’d gone after being out drinking”.

Most of the men, however, were able to describe other circumstances when the use of post-exposure prophylaxis would have been warranted but was not sought. Generally, the sexual behaviour and partner was not perceived as being of sufficient risk. One participant described his decision to access treatment on this one occasion, but not others, in these terms: “What was different? To be honest nothing - apart from they didn’t tell me they had HIV. So they might as well have been positive and they just didn’t tell me.”

Unprotected anal sex with other partners was widely reported. However, the men reported that they “trusted” their partners or that it occurred within the context of a relationship. Deciding to take a risk was rarely founded upon mutual HIV testing. The investigators therefore conclude that gay men often fail to access post-exposure prophylaxis because they do not perceive a sexual encounter to have been high risk enough, despite the fact that it carried a high risk of HIV exposure.

There was no indication that use of post-exposure prophylaxis increased sexual risk behaviour or that it was thought of as a replacement for other methods of HIV prevention. Indeed, the idea that such treatment was a kind of “morning after pill” was abhorrent.

However, there was a willingness to attribute such beliefs to other gay men, which the investigators believe is further evidence of a willingness to “other” sexual risk behaviour.

In their discussion of their findings, the investigators ask how many other MSM are involved in similar exposure events and yet do not have the same triggers for presenting to clinic. “Extra work needs to be targeted at understanding [PEP] among men who have sex with men and improving the accuracy of subjective calculations,” they said.


  1. Grulich A et al. Non-occupational post-exposure prophylaxis against HIV (NPEP) and subsequent HIV infection in homosexual men: data from the HIM cohort. Sixteenth international AIDS conference, Toronto, abstract TUPE0434, 2006
  2. Creticos C et al. Feasibility of easy post-exposure prophylaxis (PEP) for HIV prevention in high-risk men. Sixteenth international AIDS conference, Toronto, abstract THPE0449, 2006
  3. Sayer C et al. Will I? Won’t I? Why do men who have sex with men present for post-exposure prophylaxis for sexual exposures? Sex Transm Infect 85:206-211, 2009
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.