Scientists Frustrated in Search for Genital Herpes Vaccine

Stanberry said final results from the trial should be available by 2009, and -- if the vaccine proves effective -- a shot might be approved by 2010.

However, like most modern vaccine trials, the Herpevac trial relies on a piece or "subunit" of HSV to prime the human immune system against incoming virus.

Another researcher is advocating the use of the live -- but greatly weakened -- form of the virus, instead.

The problem with the subunit approach is that its effects don't last, said William Halford, a virologist at Montana State University, in Bozeman. "Once you deliver it into someone's body, it's there, but, in a few weeks, it is gone," he said.

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Live virus vaccines have a long and effective history. In fact, one of the few effective vaccines against any herpes strain -- the chickenpox/shingles (herpes zoster) shot -- was developed from live virus back in the 1960s.

Since that time, doctors have gotten more skittish about injecting people with a live form of the virus, however, so the subunit approach took precedence.

But Halford believes it is time to revisit the idea of a live virus herpes vaccine.

"All we really have to do is to figure out a way to take away some of the genes or proteins that the virus needs to cause actual disease," he said. In other words, people would be infected with a very weak form of HSV, one that is sufficient to trigger a sustained immune response but too frail to trigger disease outbreaks.

Halford is specifically investigating a protein in HSV called ICP0. "If I take away the gene that codes for that protein, the virus is really weakened," he said.

The approach is controversial, but Corey believes it could have promise. "I certainly think that the live attenuated virus is a viable approach to talk about," he said.

Funding will be the real challenge, however, whatever the vaccine strategy. According to Corey, a series of expensive failures over the past two decades has dampened the enthusiasm of industry to invest in HSV vaccine research.

"I can give my own scenario in which we worked with [drug maker] Chiron and spent seven years and a lot of money -- decapitalizing the company by 25 percent -- on an antibody-based vaccine," Corey said. "At the time, we thought it would be sufficient to work, but it didn't."