Prophylaxis Fails to Prevent HIV in Women

There were 33 HIV infections in the women on active medication and 35 infections on women in the placebo group. The participants were from the sub-Saharan nations of South Africa, Kenya and Tanzania.

“Future trials and programs will need to focus on determinants of pre-exposure prophylaxis adherence by people at high risk of infection,” Van Damme said.

What is post-exposure prophylaxis (PEP)?
Post-exposure prophylaxis is antiretroviral drug treatment that is started immediately after someone is exposed to HIV. The aim is to allow a person’s immune system a chance to provide protection against the virus and to prevent HIV from becoming established in someone’s body. In order for post-exposure prophylaxis to have a chance of working the medication needs to be taken as soon as possible, and definitely within 72 hours of exposure to HIV. Left any longer and it is thought that the effectiveness of the treatment is severely diminished.

Post-exposure prophylaxis (PEP) usually consists of a month long course of two or three different types of the antiretroviral drugs that are also prescribed as treatment for people with HIV. As with most antiretrovirals these can cause side effects such as diarrhoea, headaches, nausea/vomiting and fatigue. Some of these side effects can be quite severe and it is estimated that 1 in 5 people give up the treatment before completion. The most common drugs prescribed for post-exposure prophylaxis are zidovudine, lamivudine and nelfinavir.

Does post-exposure prophylaxis work?
Post-exposure prophylaxis has been studied in animal trials and human trials. The evidence from each individual study is not enough to confirm whether post-exposure prophylaxis works or not. However, the cumulative evidence is enough to suggest that PEP might be effective in reducing the risk of HIV infection. This conclusion is widely recognised and as a result, a number of countries have produced guidelines suggesting the possible use of post-exposure prophylaxis in both occupational and non-occupational circumstances. They tend to suggest that, as it is not guaranteed to work, post-exposure prophylaxis should only be used as a very last resort.

“It is likely that, as the researchers suggested, adherence issue were the main reasons this trial failed,” said Wafaa El-Sadr, MD, professor of clinical epidemiology at Columbia University in New York City, said. El-Sadr did not participate in the trial, but acted as moderator of the press briefing.

Who can benefit from post-exposure prophylaxis?

Since the beginning of the 1990s in most areas of North America and Europe, post-exposure prophylaxis has been available to health workers as an important aspect of safety in the workplace. In 2005, clinical guidelines from the United States Department of Health and Human Services (HHS) were drafted to extend the recommendations on using PEP to non-occupational circumstances. Nowadays, anybody who believes they have been exposed to HIV is able to ask for post-exposure prophylaxis treatment at accident and emergency areas in hospital, through GUM or HIV clinics, and via some medical doctors experienced in treating HIV in several countries.

The question of who should receive PEP has proved to be quite controversial. Several cost-benefit analyses have revealed that providing PEP to all non-occupational exposures is not an economically efficient use of limited HIV treatment resources. PEP appears to be cost-effective only when the patient has engaged in unprotected receptive anal intercourse or when the patient knows the HIV status of the partner. However, the demand for PEP does not always reflect cost-effectiveness. A ten year review of non-occupational PEP requests recorded at a Swiss clinic found an 850 percent increase in the number of people requesting PEP in the ten-year period and 58 percent of requests were for heterosexual exposure.

Guidelines released in 2011 by the ‘British Association for Sexual Health and HIV PEPSE Guidelines Writing Group’ outlined the circumstances that may warrant the use of PEP. The recommendations, specific to the UK, consider the risk of HIV infection associated with certain factors; for example how the individual was potentially exposed, the HIV status of the ‘source’ individual and whether they are from a high or low prevalence area.

Some believe that the increasing availability of PEP will lead to behavioural changes. The theory is that if PEP is readily available people will be less likely to use condoms or will be less cautious, knowing that there is a potential back up.

It has also been suggested that if PEP is available more widely, people may use PEP repeatedly. However, various studies have shown that increasing awareness and availability of PEP does not lead to increasing risky behaviour. There is also little evidence showing that people would frequently rely on PEP, probably due to the adverse side effects that the treatment can involve. In particular a study in the US showed that ‘people reduced their risk behaviour after using PEP, rather than increasing it’.

She told MedPage Today that even though the trial may have been compromised by failure of the women in the study to take their medications the study results should not be discounted. “This study shows what happens in the real world,” she said. “It is a very relevant study for this population.”


Primary source: Conference on Retroviruses and Opportunistic Infections
Source reference: Van Damme L, et al, “The FEM-PrEP Trial of Emtricitabine/Tenofovir Disoproxil Fumarate (Truvada) among African Women” CROI 2012.

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