Helpful or harmful? A drug that you can take before and after sex can help people cut their risk of HIV infection. Men and women in the United States can already take the drug as a daily pill. The new on demand regime could make the drug more convenient, and cheaper to use regularly, yet not everyone is convinced. Some doctors fear the approach will discourage condom use, while others, such as Michael Weinstein of AIDS Healthcare Foundation, see it as a free pass to promiscuity. We should abandon such moralising for the sake of public health. This will be a powerful tool for almost eliminating HIV transmission, says Cécile Tremblay at the University of Montreal, Canada. If we combine it with other measures we could reach that goal in developed countries within ten years. The medicine in question is called Truvada. It contains two antiviral drugs, also given to people infected with HIV, which stop the virus multiplying. Tremblay and her colleagues followed 400 gay men over nine months and showed that the drug reduced risk of infection by 86 per cent when taken just before sex and for two days after, and so was just as effective as the daily pill. On the face of it, having any kind of unprotected sex seems risky. Yet Truvada users are making highly nuanced decisions about their risks, argues Sheena McCormack of University College London, who helped run a trial of daily Truvada. In the West, such pre-exposure prophylaxis, or PrEP, has mainly been studied in gay men. Most trial participants used condoms some of the time, only forgoing them when it seemed safe, after asking their partners when they were last tested and when theyd had unsafe sex. PrEP may paradoxically reduce risk-taking in some. If anything, I probably use condoms more now than I did before, says Colby Briggs, a project manager at McGill University in Montreal. Taking Truvada reminds you that youre not infallible. One trial of daily Truvada showed that the drug did reduce condom use, yet STD rates stayed the same, perhaps because people were good at assessing their partners sexual history. Its less clear how well PrEP works in people having heterosexual sex. PrEP is not the only tool that we have for reducing the spread of HIV. We could put everyone who has HIV onto antivirals, which can suppress the virus, making it less likely to be passed on. In theory, such universal treatment could eradicate HIV. Its an expensive goal: The World Health Organizations aim of suppressing HIV in three-quarters of those infected by 2020 is unlikely to be met. Sub-Saharan Africa and the US have suppressed the virus in 30 per cent of those with HIV; the UK and Australia have reached 60 per cent. Combine universal treatment with PrEP and we could reduce transmission much faster, says Tremblay. Yet access to PrEP is patchy. In the US, where Truvada has been licensed since 2012, a third of doctors have never heard of it. Its also expensive: in the UK it costs about £400 for 30 pills. Some people are inevitably buying it online for about a tenth of the cost. Thats a false economy for the UKs National Health Service, says McCormack, because those users may not have the regular HIV tests that are a crucial part of PrEP. If people do get infected on PrEP, their virus can become resistant to the two drugs in Truvada and then spread to others. In many other aspects of HIV prevention, Western countries have embraced harm reduction, in other words, accepting risky behaviours cannot always be prevented but can be mitigated. So why cant we expand that to PrEP? As Tremblay says: If we have a way to protect people from catching what can be a deadly disease, then its immoral not use it.
New Scientist, 1 December 2015 ;http://www.newscientist.com/ ;