An investigational vaccine protected some women against infection from one of the two types of herpes simplex viruses that cause genital herpes, according to findings published January 5 in the New England Journal of Medicine.
The vaccine was partially effective at preventing herpes simplex virus type 1 (HSV-1), but did not protect women from herpes simplex virus type 2 (HSV-2). Women who received the investigational vaccine had less than half of the cases of genital herpes caused by HSV-1 – 58 percent fewer – compared to women who received the control vaccine.
"There is some very good news in our findings. We were partially successful against half of the equation – protecting women from genital disease caused by HSV-1," says Robert Belshe, MD, director of the Saint Louis University Center for Vaccine Development and lead author of the study.
"It's a big step along the path to creating an effective vaccine that protects against genital disease caused by herpes infection. It points us in the direction to work toward making a vaccine that works on both herpes simplex viruses."
Both HSV-1 and HSV-2 are members of the herpesvirus family. Typically, HSV-2 causes lesions and blisters in the genital area. HSV-1 generally causes sores in the mouth and lips, although it increasingly has been found to cause genital disease.
"The results of this clinical trial were a bit unexpected," says Jack Stapleton, MD, professor of internal medicine with University of Iowa Health Care and a co-author on the study. "It was somewhat surprising that HSV-1 is now a more common cause of genital disease than HSV-2, and it's more surprising that the herpes vaccine protected women from only one of the herpes simplex viruses and not the other."
There currently is no cure or approved vaccine to prevent genital herpes infection, which affects about 25 percent of women in the United States and is one of the most common communicable diseases. Once inside the body, HSV remains there permanently. The virus can cause severe neurological disease and even death in infants born to women who are infected with HSV and the virus is a risk factor for sexual transmission of HIV.
The multi-year study enrolled 8,323 women between ages 18 and 30 who did not have HSV-1 or HSV-2 infection at the start of the study. They were randomly assigned to receive either three doses of the investigational HSV vaccine that was developed by GlaxoSmithKline (GSK) or a hepatitis A vaccine, which was the control. More than 500 women participated in the study at the University of Iowa.
The clinical trial of the investigational genital herpes vaccine was funded by the National Institute of Allergy and Infectious Diseases (NIAID) and GSK, and was conducted at 50 sites in the U.S. and Canada.