By contrast, about 3 percent of a similar group of men who received neither the drug nor condoms or counseling would be expected to contract HIV over the same period.
"If you did nothing, you would expect at least 3 percent of men to get infected, particularly if you're talking about young men," said one of the study's principal investigators, Dr. Kenneth Mayer, medical research director and co-chair of The Fenway Institute at Fenway Health in Boston, one of the sites participating in the study.
Side effects included nausea, headaches, weight loss and elevated levels of creatinine (a naturally occurring molecule filtered by the kidneys). The researchers say that while adverse events were similar between Truvada users and non-users, more people who took the pill suffered from nausea.
Mayer believes that adherence might actually go higher in the real world, now that the efficacy of the drug combo has been shown.
"There was no human data before that said taking pills in advance would protect you. Now we have the data," he said.
"Protection was over 90 percent when the drug was in the body," Mayer said. "That says to us that we can probably do better in adherence. People may be more motivated to adhere once they [see these results]."
But translation into the real-world would take a "massive commitment" of federal dollars along with concerted efforts on the parts of communities to reach out to a vulnerable population which often mistrusts the health-care system, Horberg said.
There's the cost for the medication, for one thing: A year's worth of Truvada totals more than $10,000 a year, and that is the discounted rate, Mayer said. Although generic versions are available in some countries (not the United States) for as low as $500 a year, he added.
Researchers are now looking at wheth
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