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Case report
Overlapping HIV prevention strategies; case report of pre-exposure and postexposure prophylaxes used for a single risk event between two men
  1. Don E Smith1,2,
  2. Jill Gardiner1,
  3. Rebekah Oliver1,
  4. Damien Fagan1,3
  1. 1Albion Centre, South Eastern Sydney Local Hospital Network, Sydney, Australia
  2. 2School of Public Health and Community Medicine, UNSW, Australia
  3. 3Discipline of Pharmacy, Faculty of Health, University of Canberra, Canberra, Australian Capital Territory, Australia
  1. Correspondence to Damien Fagan, damien.fagan{at}


A range of prevention strategies have been considered in an attempt to reduce HIV transmission. The use of continuous antiretrovirals (ARVs) in high-risk HIV-negative individuals (pre-exposure prophylaxis or PrEP) and the short-term use of ARVs following a high-risk exposure (postexposure prophylaxis or PEP) are among these strategies. We report a case of the contemporaneous use of PEP and PrEP in a sexual liaison between two men.

In an attempt to reduce the number of new cases of HIV infection, a range of prevention strategies have been advocated. Prior to the availability of ARV therapy, the key prevention measure was condom promotion and modifying sexual behaviour such as partner number reduction within high-risk groups. This was followed by: the introduction of PEP, treating all HIV cases with ARVs to reduce the probability of transmission (treatment as prevention) and in the past few years the use of PrEP. Case-control, observational and randomised clinical trial data exist to support these strategies. We describe what we believe is the first reported use of PrEP and PEP in a sexual liaison between two men in Sydney.

  • HIV

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Patient X, a clinician in his late thirties, presented to our service requesting postexposure prophylaxis (PEP) following an episode of unprotected insertive and receptive anal intercourse with a casual male partner the previous evening.1–3 Patient X decided not to use condoms as the partner told him he was taking tenofovir 300 mg/emtricitabine 200 mg as PrEP, even showing him the medication bottle. However, the next morning patient X(with some background in HIV medicine) recalled some evidence regarding the protective effects of PrEP; namely that in the iPrex study it was found to have only a 43% protective effect compared with placebo, but closer to 92% protective in fully compliant subjects.4 As he was unable to verify the source’s compliance and worried that the source may have engaged in multiple casual sexual acts in the belief he was protected from HIV, patient X became anxious. The patient had last tested negative for HIV 3 weeks earlier, and had no other risk events in the preceding 3 months. A baseline HIV antibody/antigen test was negative and he was prescribed a course of zidovudine/lamivudine for 1 month as PEP in accordance with local guidelines.5 Follow-up serology at 1 month and 3 months confirmed that HIV infection has not occurred.


PrEP is the latest in a suite of prevention strategies against HIV transmission, each with variable levels of success. In New South Wales in the 1980s the extensive promotion of condoms and reducing partner numbers resulted in a huge reduction in HIV incidence, flat-lining at around 350 new cases per year for many years.6 Despite a universal healthcare system where antiretrovirals (ARVs) are fully funded and clinician visits and pathology testing is provided by federal and state health services, allowing extensive ARV coverage, the number of new cases of HIV has unfortunately risen in recent years. Strategies such as government subsidised provision of PEP has not resulted in a decline in HIV rates, with research from Sydney showing that receipt of PEP actually increases the risk of subsequent HIV acquisition.7

Tenofovir 300 mg/emtricitabine 200 mg is the most commonly prescribed agent used in PEP and PrEP, and costs approximately $A750 per month of treatment. There is potentially a significant risk that widespread uptake of PEP and PrEP will provide a false sense of security to people engaging in high-risk sexual encounters and will result in provision of expensive medication to individuals who actually have low risks of HIV acquisition. In patient X's case the estimated risk of HIV infection from unprotected anal sex with a known HIV+ source would be in the region of 1.4%8; the prevalence of HIV infection in men who have sex with men populations in Sydney is estimated to be 9.1%,9 meaning that approximately 785 similar exposures would need to receive PEP to prevent a single infection. However, if the source were receiving PrEP, with estimates of 43–95% efficacy,4 this would expand to between 826 and 1828 prescriptions of PEP needed to prevent one transmission. Should PrEP uptake increase within our local men who have sex with men population, it is likely that PEP guidelines will have to change to maintain relevance and cost-effectiveness.

Key messages

  • The limited evidence supporting postexposure prophylaxis is further diminished when pre-exposure prophylaxis is also available.

  • The introduction of government funded pre-exposure prophylaxis among high-risk men who have sex with men will alter the cost-effectiveness of postexposure prophylaxis where these programmes overlap. Research is needed to redefine risk exposure in this context.



  • Contributors DES, JG and RO contributed to the writing of this case report as well as being directly involved in this patient's care. DF contributed to the writing of the case report.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.