A government-funded study testing a herpes vaccine is under way at more than 20 sites across the United States. The study of 7,500 women will examine whether the vaccine, given in three doses within six months, can prevent infections in women ages 17 to 35 who have not been exposed to either HSV-1 or HSV-2.
Earlier studies of the vaccine showed it wasn't effective in women who were already exposed to either or both of the viruses. It also didn't work in men. But it was found to protect against infection in more than 70 percent of women who weren't previously exposed to HSV-1 or HSV-2.
Experts aren't sure why the vaccine doesn't work in men. However, if the vaccine is eventually approved in women, widespread immunization could help protect men, too, says Dr. Joel Ward, director of the Center for Vaccine Research at the University of California, Los Angeles.
"If it's not circulating in the population, then men won't get herpes," Ward says.
The study is scheduled to conclude next year and, if successful, would be the second vaccine against a sexually transmitted disease. A vaccine against human papilloma virus, which can cause cervical cancer, was approved this year for use in girls and women ages 9 to 26.
How well that vaccine, called Gardasil, is accepted by the public may point to the success of a future herpes vaccine, experts say. Vaccines for STDs need to be administered in childhood, well before the initiation of sexual activity. But parents may prove reluctant to consider their child's risk for infection later in life.
"Everybody is interested in what the public response will be to Gardasil," says Dr. Judy Falloon, the chief medical officer for the herpes vaccine trial at the National Institutes of Health. It may be harder to convince parents of the importance of a herpes vaccine, she says. "HPV can be thought of as a cancer vaccine. It doesn't have the stigma of an STD. Herpes is very stigmatized."
Ward believes that once parents understand the benefits, they won't hesitate to protect kids from any potential threat.
"Over the next few years, young teens, ages 10 to 12, will be offered a number of vaccines that can make their adult years safer than our adult years," he says. "If I can prevent anything, why not do it?"