A study involving nearly 2,500 HIV-negative men and transgender women having sex with men showed that a once-daily regimen of a combination pill containing two antiretroviral drugs (tenofovir and emtricitabine) can act as a good pre-exposure prophylaxis and prevent HIV infection. The two drugs are already being used for treating HIV/AIDS. The study was done in six countries — Brazil, South Africa, Thailand, the United States, Ecuador, and Peru. The study published online recently in The New England Journal of Medicine (“Preexposure chemoprophylaxis for HIV prevention in men who have sex with men,” by Robert M. Grant, et al.,) showed that the overall efficacy of the drug was 47 per cent. The protection level was 73 per cent when the drug compliance was 90 per cent or more. This demonstrated that a drug taken as pre-exposure prophylaxis can partly protect gay men from HIV infection. This is not the first time that antiretroviral drugs used as prophylaxis have been found to protect people against infection by the virus. In fact, their efficacy in preventing vertical transmission from HIV-infected pregnant woman to child has been proved beyond doubt, and the drugs are routinely being used today. A trial conducted in Botswana showed that providing infants with prophylactic antiretrovirals greatly reduced the chances of their contracting the infection through breastfeeding — nearly 40 per cent of HIV-infected children get the disease this way. The use of tenofovir as a microbicide was recently shown to provide 54 per cent protection where women used it more than 80 per cent of the time.

But unlike in these cases, the daily use of antiretroviral drugs as a prophylaxis by men who have sex with men should never be considered as a silver bullet even though the protection level can be as high as 73 per cent. A major concern is the real possibility of developing drug resistance from daily consumption of the drugs, especially by those who are already infected with HIV, as the trial revealed. Although reversible on discontinuation of medication, renal problems developed by a small fraction of volunteers turn the spotlight on the toxic effects associated with daily exposure to the drug for prolonged periods. These challenges can be partly overcome if intermittent use of antiretroviral drugs by gay men proves to be equally effective. A couple of clinical trials are currently under way to test this hypothesis. But irrespective of their outcome, proven methods such as abstinence, confining oneself to one partner, and using condoms during every sexual encounter should remain the cornerstone of HIV prevention.

More In: Editorial | Opinion