An experimental vaccine for genital herpes may help limit the spread of the incurable disease, which afflicts one in five adult Americans.

The vaccine prevented infection in 74 percent of women exposed for the first time to the genital herpes virus, known as herpes simplex virus type 2, according to the article, "Glycoprotein-D -- Adjuvant Vaccine to Prevent Genital Herpes," published in today’s New England Journal of Medicine (2002;347(21):1652-1661). But the vaccine did not work at all in men, researchers reported, adding they were not sure why.

GlaxoSmithKline, which developed the vaccine, said the results of the study were so promising that a final-stage study will be launched, testing the vaccine on 7,550 women ages 18 to 30 around the United States. If the new tests bear similar results, the vaccine could be available in about five years, said Lawrence Stanberry of the University of Texas Medical Branch in Galveston, who led the study.

Stanberry’s team studied 978 women and 1,736 men whose partners had genital herpes, all of whom got either three vaccine shots or three placebo shots within a six-month period. They were followed for a total of 19 months. The researchers discovered the vaccine did not work well in women who had been infected by a related virus, the herpes simplex virus type 1. Only when women had never been exposed to type 1 or type 2 herpes did the effectiveness of the vaccine reach 74 percent.

The STD can cause painful itching and sores that in some cases reappear for years. But most of the 45 million infected Americans have no symptoms, helping to spread the disease between sexual partners, who are often unaware they are carrying the virus. Herpes is a risk factor in the spread of HIV and can be fatal for infants infected during birth.

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