First data showed no evidence that the pill worked.
Women who were the drugs, Truvada, are just as likely as it infected see a placebo to win an independent panel that analyzed had the results, after half the 4,000 women took the study about, which researchers had hoped.
Of the 1,900 women, the Truvada or a placebo had 28 in each group to become infected than last week, according to FHI, formerly family health international, the non-profit group which carried out the study in South Africa, Kenya, and Tanzania.
"It is surprising, disappointing and frustrating," said Mitchell Warren, Executive Director of AVAC, an advocacy group for AIDS prevention in New York. "But there is a strong justification for the continuation of other studies in women in the hope of better results in future get."
Two other studies of so-called "pre exposure prophylaxis" in women are still under way in Africa. The results are expected in the next two years.
The latest study inconclusive results are a surprise of many experts. A study published in November last year found that protected Truvada gay men against infections. Men who faithfully took their pills have been shown, better than 90 percent protection, have celebrated a result as a breakthrough for AIDS prevention.
And last summer from a study in South Africa published results showed that a vaginal gel with tenofovir, one of two antiretroviral drugs in Truvada, reduces the risk of infection by 54 percent in women who use it reliably before and after sex.
Because the current study - known has been stopped as FEM-PReP on the list of scientists, use catchy acronyms to differentiate many similar studies - early and abruptly, remain many questions about it.
One is whether there was a difference in how often the women Truvada and those who actually took their pills placebo. More women who complained of unpleasant side effects, and therefore may be more to the program to keep failed Truvada.
The researchers asked the women each month as often took their pills, but preferred by blood samples to confirm the answers. The samples are in the store and has not been analyzed.
After that is done, "We get better grip the compliance with, may be", said Dr. Timothy Mastro, Vice President for health and development Sciences of FHI.
Is removed each woman who became pregnant from the trial, because Truvada is not safe for pregnant women; for unknown reasons, taking the medication more women became pregnant, which may have distorted the early results.
Another question is how much infused Truvada the walls of the vagina, where the initial infection takes place.
According to Dr. Robert M. grant, a California AIDS researchers, the study of Truvada in gay men, led, other research has shown that vaginal gels are as in the vaginal walls 100 times more effective than pills always protected anti-retroviral drugs. Pills and gels are about equally effective in they get in rectal tissue, he said.
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