The hope was that people would have a strong natural defense against herpes, and could withstand direct exposure and resist infection. Chiron's approach took the parts of two proteins from the viral coat, along with an immune-boosting substance, and created a vaccine that proved capable of causing marked increases of antibodies against herpes. But in the end, the vaccine failed to protect against the virus. Researchers, lead by Lawrence Corey, M.D., of the University of Washington in Seattle, report that in the first 150 days of the trials, there was a consistent drop in the number of people infected with the virus. This decreased acquisition rate suggests that the vaccine was working to a degree in the early stages, but then the protection disappears.
Researchers report it was unclear why the immune response disappeared.
Researchers also think that recurrent exposure to the herpes virus may have something to do with why the vaccine failed. Lab studies did not examine multiple sexual exposures to the virus. Researchers believe that the vaccine failed slightly with every exposure, eventually resulting in its ineffectiveness. Aside from the disappointing results, Corey et al. state that the trials themselves may be an important model for future vaccine trials. More than 2,000 people at 40 centers participated in the trials that lasted for up to four years.