HealthDay News — None of 657 patients who took a daily pill to prevent HIV infection contracted the virus over a period of more than two years, according to a study from Kaiser Permanente of San Francisco. The findings, published online in Clinical Infectious Diseases, dispel concerns that use of pre-exposure prophylaxis (PrEP) would lead to more HIV infections, The New York Times reported.

Gay men accounted for all but four of the patients who took the two-drug combination (emtricitabine and tenofovir [Truvada]), which was approved by the U.S. Food and Drug Administration in mid-2012. The patients were followed from then until February of this year, and 84% said they had multiple sexual partners during that time, The Times reported.

More than 40% did say they used fewer condoms and some were infected with other sexually transmitted diseases such as syphilis, gonorrhea, and chlamydia as a result, but none contracted HIV. “This is very reassuring data,” lead author Jonathan Volk, MD, an epidemiologist at Kaiser Permanente of San Francisco, told The Times. “It tells us that PrEP works even in a high-risk population.”

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“This shows that the effectiveness of PrEP is really strikingly high,” Anthony Fauci, MD, director of the U.S. National Institute of Allergy and Infectious Diseases, told The Times. “And this study takes it out of the realm of clinical trials and into the real world.”


  1. Volk JE et al. Clin Infect Dis. 2015; doi: 10.1093/cid/civ778.
  2. Koester KA Grant RM. Clin Infect Dis. 2015; doi: 10.1093/cid/civ783.