Gels containing microbicides have been praised as the miracle weapon against catching HIV infection, as they could have been used by the women in the third world by themselves, without the man's agreement, to protect themselves against infection during the sexual act.

The gels are applied intravaginally.

Now, trials of a new type of gel developed to help women protect themselves from HIV were stopped on Wednesday after women employing it got infected by HIV at a higher level than women not using it, as investigators discovered.

The experiments were made on 1333 women in South Africa, Benin, Uganda and India.

"The microbicide gel apparently made the women more vulnerable to the virus, not less vulnerable as intended," said its makers Polydex Pharmaceuticals, based in Toronto, Canada.

The microbicide gel was branded with the name Ushercell, and is a cotton-based product that had been checked in more than 500 women without any adverse effect about the risk of HIV infection.

A second testing experiment for the same product has also ceased its checks in 1700 women in Nigeria, out of concern for the women's life, even if in this case, the analyses did not point a higher-than-expected virus infection.

Women who got infected during the trials will receive anti HIV medication, as announced by the researchers.

"While the findings are unexpected and disappointing, we will learn scientifically important information from this trial that will inform future HIV prevention research," said Lut Van Damme, who was leading the trial of the Polydex product.

This is the second time when trials with a microbicide anti HIV vaginal gel or cream suffer spectacular failure.

The other failed product is spermicide nonoxynol-9, although it is still unclear why the product did not work and moreover, increased the risk of infection.

There are other three products in advanced trials, the last one being based on a seaweed chemical called carrageenan.