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A ‘morning after’ pill for HIV prevention?

Indian social activists and children released a World AIDS Day awareness sign tied with ballons in Kolkata on Tuesday. (Byangshu Sarkar/AFP/Getty Images)
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U.S. health officials have launched a major push to get those at risk of getting HIV to take a prevention pill known as Truvada. According to current recommended practices you're supposed to take it every day for it to work most  effectively. But what would happen if you just took it at key moments -- such as before and after having unprotected sex?

An intriguing new study in the New England Journal of Medicine tested that idea on 400 high-risk gay men and transgendered women and found that it just might still help.

Similar to the idea behind the "morning after" pill, a high dose of birth control pills taken after unprotected sex to stop pregnancy, the study involved taking a double dose of Truvada before and after unprotected sex to prevent the virus from establishing a hold.

The participants, who were recruited from France and Canada, were randomized in double-blind trials into two groups, with one taking two placebos two to 24 hours before and two to 24 hours after unprotected sex and the other taking two doses of Gilead's Truvada, which is a combination of the two anti-HIV drugs tenofovir disoproxil fumarate and emtricitabine. The participants took a median of 15 pills per month.

Researchers followed them for a median of 9.3 months and found that a total of 16 people became infected with HIV. Two were in the medication group and 14 in the placebo group. That pointed to a relative reduction in risk of 86 percent for those on Truvada.

The study, which was funded by Gilead, which makes Truvada, did not directly compare taking the pill daily to taking it only as needed. Given this limitation, its small sample size, the lack of diversity in the population and the short duration of the follow-up, the results should be considered very preliminary.

"This finding is among the highest risk reductions that have been reported to date, but the short follow-up for our study may have increased the likelihood of an exaggerated estimate of efficacy due in part to high initial adherence," lead author Jean-Michel Molina and his co-authors wrote.

But the idea of being able to take the prevention pill on-demand poses huge advantages, ranging from the cost to individuals and the public health system to reducing potential side effects. The results are so promising that there are likely to be numerous follow-up studies in the coming years on alternative ways of taking Truvada.

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