ViewpointPre-exposure prophylaxis for HIV infection: what if it works?
Section snippets
Pre-exposure prophylaxis
Disease prevention by prophylactic drugs is standard practice in travellers to malaria-endemic countries and for other infections such as Pneumocystis jirovecii in HIV infection. Various studies11, 12, 13, 14 show that antiretroviral treatment given at or shortly after an exposure can substantially reduce HIV transmission: prompt treatment clearly increases effectiveness.15 This observation led to the hypothesis that transmission could be decreased further if treatment was delivered before
Drug toxicity and viral resistance
Tenofovir (and tenofovir and emtricitabine) has a good safety profile and infrequent side-effects; the most common side-effects are gastrointestinal discomfort, dizziness, headache, and rash. Less than 1% of patients with HIV taking tenofovir in clinical trials had serious drug-related adverse events such as acute renal failure, Fanconi's syndrome resulting in severe hypophosphataemia, decreases in bone-mineral density, and rarely, lactic acidosis.22 Tenofovir plus emtricitabine has the same
Increased risky behaviours
Mathematical modelling of HIV transmission by people taking antiretroviral drugs suggests that reduction or reversal of any benefits could result from a small increase in risky sexual behaviour.26, 27 Although pre-exposure prophylaxis might greatly reduce HIV transmission, this effect could diminish if people taking such prophylaxis increase their risky behaviour. Moreover, HIV prophylaxis offers no protection against other sexually transmitted infections.
Present trials should provide data for
Ethics
The possibility of pre-exposure prophylaxis for HIV raises important ethical questions such as: what are the obligations of governments and industry to provide such prophylaxis? How should resources be distributed between research, treatment, counselling, testing, primary prevention, pre-exposure prophylaxis, and post-exposure prophylaxis? Who should have priority for prophylaxis? These types of issues arise in many health-care settings; however stigma associated with HIV poses particular
Public-health issues
Mathematical models of pre-exposure prophylaxis35 and topical anti-HIV microbicides,36, 37, 38 suggest that even a partially effective product could avert many infections. The trials of pre-exposure prophylaxis will provide important safety and efficacy data for prevention of HIV transmission by injecting drug users and through sexual intercourse. However, even after these trials conclude many information gaps will remain. Perhaps most important is that not all groups at risk are included. For
Steps to take today
In August, 2006, the Global HIV Prevention Working Group, an international panel of more than 50 experts on HIV and AIDS, was convened by the Bill and Melinda Gates Foundation to discuss HIV-prevention research, and released a report about factors necessary for enabling access to new HIV-prevention technology. These factors include early commitment of resources from donors, coordination between governments and regulatory agencies, and planning of guidelines for use.39 Although the first results
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