Treatment as prevention (TasP) can refer to several bio-medical strategies. In both pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP), HIV-negative people take daily regimens of antiretrovirals (ARVs) to reduce the risk of a possible infection. In prevention of mother-to-child transmission (PMTCT), pregnant women with HIV take meds so the virus isn’t passed to their babies.
Last but not least, TasP also can refer to the idea that treating people with HIV not only improves their health but also prevents transmission of the virus. It’s this notion of TasP that most people seem to associate with the phrase—and it’s this aspect that remains the most misunderstood.
The concept has been floating around for years—after all, if ARVs dramatically reduce the virus in bodily fluids, then it follows that HIV is less likely to be spread during sex—but it gained backing five years ago with the so-called “Swiss Statement.” Authored by four of that country’s HIV experts, it claimed that an HIV-positive person on ARVs and with an undetectable viral load and no sexually transmitted infections cannot transmit HIV through sexual contact.
The statement, however, was based on “review of the medical literature and extensive discussion.” In 2011, the supporting data arrived from the HIV Prevention Trials Network when its HPTN 052 trial found that, for heterosexual couples, starting early treatment led to a 96 percent reduction in HIV transmission to the negative partner. The news made global headlines. The journal Science named it “the 2011 Breakthrough of the Year,” and Time magazine listed treatment as prevention as the year’s No. 3 medical breakthrough.
In December 2012, Chinese scientists claimed that TasP indeed prevented infections—but by 26 percent, not 96. So which is it? What’s more, given that anal sex is 10 to 20 times riskier than vaginal sex and that the studies were based on heterosexuals, how do the findings apply to gay men? The flood of recent data might seem overwhelming, but on closer inspection, a clearer picture emerges on the horizon.
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