A global push to get women with HIV prevention tools has once again suffered a setback, final results from a four-year study that sought to determine the safety and effectiveness of two antiretroviral (ARV)-based HIV prevention approaches in women show.

Speaking to journalists in the trial countries of Uganda, Zimbabwe and South Africa via teleconference on Monday, the lead researchers announced that none of the three products - tenofovir gel, oral tenofovir and oral Truvada - proved to be effective among the women enrolled in the VOICE study.

"These results are disappointing but it is clear that daily use (gel or tablet) is not the right approach for women like those in VOICE (mostly young and unmarried); adherence was very low," said Dr Jeanne Marrazzo of the University of Washington who was due to present the results at the ongoing 20th Conference on Retroviruses and Opportunistic Infections (CROI) in Atlanta, USA.

According to the study results, the drug was detected in less than a third of blood samples from women who were assigned to use either Truvada or oral tenofovir and in less than a quarter of samples from women designated to use gel. Carried out at 15 sites in the three countries involving a total of 5,029 women, the VOICE study was designed in a way that saw participants enrolled either in groups taking a daily tablet (Tenofovir or Truvada) in what was called oral pre-exposure prophylaxis (PrEP) or in the group that used the Tenofovir vaginal gel daily.

Testing of the daily use of Tenofovir tablets and Tenofovir gel was stopped in September 2011 and November 2011 respectively after routine independent reviews of data showed while both products were safe, they were not effective in guarding women against HIV infection. However, it was not known until yesterday that all the three products including Truvada whose testing was allowed to continue through the end of the study failed because women simply failed to use the products on a daily basis as per the study design.

In explaining the results, the Microbicides Trials Network (MTN) which designed the study observed in a statement that although the VOICE outcome was disappointing, VOICE has proven that daily use of a product - whether a vaginal gel or an oral tablet - is not the right HIV prevention approach for African women like those in VOICE, who were predominately young and unmarried.

Compared to older, married participants, single women under the age of 25 were least likely to use their assigned products and most likely to acquire HIV. The results, researchers conclude, underscore the significance of adherence to usage.

A snapshot of the Uganda results shows that nine out of 322 participants who were enrolled at the only site that Uganda had, acquired HIV during the study, representing a 2.1 per cent HIV incidence rate.