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Can the promotion of post-exposure prophylaxis following sexual exposure to HIV (PEPSE) cause harm?
  1. J Richens1,
  2. S G Edwards1,
  3. S T Sadiq2
  1. 1Centre for Sexual Health and HIV Research, The Mortimer Market Centre, Mortimer Market, London WC1E 6AU, UK
  2. 2Courtyard Clinic, St George’s Hospital, Blackshaw Road, London SW17 0QT, UK
  1. Correspondence to:
 John Richens
 Centre for Sexual Health and HIV Research, The Mortimer Market Centre, Mortimer Market, London WC1E 6AU, UK;

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Health policy decisions should be based on sound evidence

Sustained increases among homosexual men of unsafe sexual behaviour, sexually transmitted infections, and HIV have caused much concern.1 HIV transmission among homosexual men continues despite the use of antiretroviral therapy that lowers infectiousness.2 The idea that “treatment optimism” has led to “behavioural disinhibition” has attracted much attention although recent data suggest it is by no means the whole story.3

Guidelines for the administration of antiretroviral drugs as post-exposure prophylaxis following non-occupational or sexual exposure (termed nPEP in the United States and PEPSE in the United Kingdom) have been drawn up in both the United Kingdom4 and the United States.5 These guidelines offer advice on when to give prophylaxis and to whom. Both guidelines acknowledge that the evidence in support of the recommendations is not watertight. Much of the evidence is inferred from retrospective data on occupational exposure,6 the use of antiretroviral therapy to reduce mother to child transmission of HIV,7 and on experimental simian immunodeficiency virus (SIV) and HIV-2 infections in macaques.8,9 The data suggest that PEPSE can reduce the risk of infection with HIV if administered promptly (less than 72 hours after exposure) and continued for 28 days. A non-randomised study among 202 homosexual men provided with access to PEPSE in Brazil suggested that there were 81% fewer seroconversions among those who took medication but was still not conclusive.10 Other research suggests most homosexual men who receive PEPSE are more careful for periods of up to two years.11 Waldo et al were unable to demonstrate that the availability of PEP in San Francisco was increasing risk behaviour in homosexual men generally.12 The most recent health economic evaluation of PEPSE in the United States has concluded that PEP for sexual or injection drug exposure would be cost effective across 96 metropolitan areas.13 In general, studies suggest that maximum cost effectiveness would be achieved if PEPSE were given following receptive anal intercourse with a partner at high risk of infection or high risk exposures with a partner known to be infected. Even in San Francisco, 217 homosexual men reporting unprotected receptive anal intercourse with a partner of unknown status would need to be treated with PEPSE to prevent one transmission.13

We believe there is a distinct danger that the promotion of PEPSE could reinforce rising trends in risky sexual behaviour and might add to, rather than lessen, HIV transmission

A question that remains unanswered is what is the effect on the highest risk behaviours at a population level, of making PEPSE available on demand. The most desirable outcome (which is presumed by both guidelines) is that promoting PEPSE will cut rates of HIV infection in exposed individuals and reinforce safer sexual behaviour. Another possibility is that the promotion of PEPSE will make no difference to the epidemic with the numbers protected being counterbalanced by additional infections in men whose risk behaviour is increased by awareness of PEPSE but who then fail to obtain it or to respond to it. This outcome is consistent with the theory of risk homoeostasis developed by psychologist Gerald Wilde which posits that where an intervention to reduce risk is introduced, any protective gains tend to be counterbalanced by losses among individuals who increase their risk exposure too much.14 Should this prove to be the case with PEPSE, as we have suggested previously,15 then evaluations of the cost effectiveness of PEPSE could reach very different conclusions.

In the central London clinic where two of us work PEPSE was given to 48 patients in 2003 and 119 in 2004. The projected cost of PEPSE drugs alone for 2005 is £180 000. Our HIV clinics are experiencing significant service and cost pressures since the introduction of the PEPSE guidelines and the publicity campaign by the Terence Higgins Trust, aimed at increasing awareness of PEPSE among homosexual men and encouraging them to approach clinics for advice. Since the start of the publicity campaign, relative increases in those obtaining PEPSE in a south west London clinic have been similar to those in north London despite this clinic not being identified in the publicity material.

The most serious question that has to be asked about PEPSE is whether it could cause net harm, protecting only a few individuals at the expense of adverse effects on behaviour and increased HIV transmission in the wider community. Increases in unsafe sexual behaviour among homosexual men have been reported in many countries in the past few years. The coincidence of this phenomenon with improved therapy has attracted much speculation and debate.1 With this background it seems legitimate to ask whether promoting PEPSE could exacerbate these trends. Clinicians, who rightly focus on helping the individual, may be reluctant to examine this possibility but it must be taken seriously when there is an expanding epidemic. We are concerned that there is pressure to make PEPSE available for homosexual men regardless of cost and without proper consideration of possible negative consequences on service delivery and HIV transmission. Local commissioners of HIV healthcare services in the United Kingdom have not been involved in decisions on the provision of PEPSE. We fear a backlash from unfavourable public opinion if large sums are to be spent without adequate evaluation on a measure of unproved efficacy at the individual level and with the potential to disinhibit safer sexual behaviour generally. Media interest could also lead to increasing numbers of heterosexuals seeking PEPSE, a situation in which PEPSE will rarely be cost effective in the United Kingdom.

Health policy decisions should be based on sound evidence. We conclude, firstly, that the scientific community has a responsibility to consider and attempt to measure the impact of PEPSE on clinical outcomes, behaviour, and attitudes, both at the individual and community level, in order to demonstrate whether it is beneficial or harmful. Secondly, until the evidence is clearer, we would question the wisdom of a national campaign publicising access to free provision of PEPSE. We believe there is a distinct danger that the promotion of PEPSE could reinforce rising trends in risky sexual behaviour and might add to, rather than lessen, HIV transmission.


This editorial was written following discussion with many colleagues. In particular we would like to thank the following for suggestions: Paul Benn, Jackie Cassell, Richard Gilson, John Imrie, Kevin Miles, Angela Robinson, Ian Weller, Mark Pakianathan, Helen Pritchitt, and Wendy Majewska.

Health policy decisions should be based on sound evidence