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When pre-exposure prophylaxis, or PrEP (Truvada), first hit the market, critics were skeptical of the pill's claims that it could keep clients HIV-free if it at the same time lured people into believing they could have safe sex condom-free. However, 657 clients and more than two years later, it looks like that has, in fact, been the case: Not one person on the pill caught the virus, The New York Times reports.

However, critics who suggested the security provided by PrEP — which is close to 100 percent successful — would lead to a false sense of security about sexually transmitted diseases appear to have been correct. Gay men in the study did use fewer condoms, and about half became infected with syphilis, gonorrhea, or Chlamydia within a year. Forty percent said their condom use decreased, although the vast majority said their number of sexual partners remained the same. At least there's this: While HIV (which can develop into AIDS) is controlled with antiretroviral drugs taken for life, most other STDs are treated with a run of antibiotics.