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Genital Herpes Health Center

New Herpes Vaccine Affects Women Only

Scientists Surprised That Vaccine Immunizes Just 1 Sex
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Both forms of the virus are incurable, and those infected may not even know it. The virus may lie dormant for years or decades, producing little or no symptoms. It is highly contagious when active.

The two studies involved more than 2,700 people in the U.S, Canada, Italy, New Zealand, and Australia between 18 and 45 years old. In both studies, the people had regular sex partners who had a history of genital herpes. Some study participants received three doses of the vaccine and others got a placebo injection -- at the start of the study, one month later, and at six months. They were monitored for 19 months.

In the first study, the 270 women and 580 men were all free of either HSV-1 or HSV-2. Compared with women getting a placebo injection, the vaccine reduced genital herpes disease in women by 73%. "But low and behold, it did pretty much nothing in men," Bernstein tells WebMD. "So we did a second study."

The team then tracked more than 700 women and 1,100 men, some of who had HSV-1 but not HSV-2 . The vaccine proved 74% effective -- but only in a subgroup of women without HSV-1. Neither the women with the "cold sore" virus nor the men were protected by the vaccine.

Though the sex disparity isn't clear, researchers say it may have to do with how HSV enters the body. In women, the virus enters through the vaginal mucous membrane -- which already is bathed in antibodies and disease-fighting T cells. "So more vaccine-induced antibodies flood to the mucous membranes for more coating," says Bernstein. "In men, the virus usually enters through cracks in their skin, which aren't bathed in antibodies."

And the HSV-1 connection? "It's not so much that the vaccine didn't work in those who have HSV-1 already," he tells WebMD. "Rather, HSV-1 itself may already provide a level of protection against the disease that is similar to that of the vaccine."

The vaccine, developed by GlaxoSmithKline, which paid for the studies, is made from a protein in the genital herpes virus. A third study, also sponsored by the drug manufacturer and now in conjunction with the National Institutes of Health, will begin this month to further test the vaccine in nearly 8,000 women between ages 18 and 30. GlaxoSmithKline is a WebMD sponsor.

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