SAN FRANCISCO (KGO) -- A recent report says a San Francisco man got HIV even though he was taking a preventative drug. There are just handful of these cases in the world.
Dr. Stephanie Cohen, medical director of the San Francisco City Clinic, spoke with ABC7 News about how this happened.
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"We think that the patient acquired HIV because the virus he was exposed to was resistant to one of the two medications that's in Truvada," Cohen said.
Truvada is used to treat people with HIV. But for people who don't have HIV, it's a preventative drug - taken regularly, Truvada can block people from getting HIV when they're exposed to the virus.
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Cohen stressed how rare it is for someone to get HIV while taking Truvada.
"This is only the sixth report of someone who's actually become infected with HIV despite taking PREP regularly," she explained. "I don't think that people should be concerned."
Doctor: Despite recent rare case, HIV prevention drug works