A vaccine thought to prevent two types of genital herpes fell short in a clinical trial, reported MSNBC.
The experimental vaccine was found to moderately protect against only one of the two types of the sexually transmitted virus in women, according to an analysis published January 5 in the New England Journal of Medicine.
“I think this is the end of the vaccine,” said coauthor Dr. Peter A. Leone, an infectious disease specialist at the University of North Carolina, Chapel Hill. “It would be difficult to imagine marketing a vaccine that would only work against HSV1.”
For unknown reasons, the vaccine protected against herpes simplex virus type 1 (HSV1) but not type 2 (HSV2). The clinical trial, Herpevac Trial for Women, studied 8,323 women ages 18 to 30 at 50 sites in the United States and Canada from 2002 through 2010, according to HealthCanal.com.
At enrollment, all participants were free of both herpes viruses. Volunteers were randomly assigned to receive three doses of either the investigational vaccine or a licensed hepatitis A vaccine, the control. Throughout the 20 months, participants were evaluated frequently for genital herpes disease, and blood tests determined if either virus occurred in the women during the study.
In earlier research involving herpes-free men and women with infected sexual partners, the vaccine prevented genital herpes disease in more than 70 percent of women with no clear effect in men.
One in six Americans ages 14 to 49 is infected with HSV2, reports the Centers for Disease Control and Prevention. Nearly 60 percent of adults in the U.S. are infected with HSV1, according to federal figures, reported MSNBC.
Despite the vaccine's shortcomings, the study did provide insight into the morphing roles of the two viral types of herpes. Traditionally, HSV-1 is associated with cold sores near the mouth, and HSV-2 with genital lesions and blisters. But the study revealed HSV-1 is increasingly causing the genital disease, observed one NEJM researcher. In the study, HSV-1 cause more cases of genital herpes than HSV-2.
The search for a herpes vaccine in not over.
“We’re going to need a different approach,” Leone said. His trial used a vaccine containing an HSV protein designed to trigger an immune response against the virus. Maybe, he said, a vaccine that uses weakened live virus -- like the chickenpox vaccine -- would work better.