AIDS researchers hoping to find a way for women to silently protect themselves from Aids infection were disappointed to report on Wednesday that tests showed one product actually worsened the risk. The product, a spermicide called nonoxynol-9 and marketed under the trade name Advantage S by US-based Columbia Laboratories Inc, did not protect women in Benin, Ivory Coast, Thailand and South Africa from infection with HIV, a team of United Nations-sponsored researchers said. “We were dismayed to find out that the group using the N-9 gel had a higher rate of HIV infection than the group using a placebo,” Dr Joseph Perriens, who heads the UNAIDS microbicide effort, said in a statement.