Results from a Phase III clinical trial found an experimental vaccine that showed early promise is not effective in preventing genital herpes disease in women.
The Herpevac Trial for Women ran for eight years beginning in 2002 and involved more than 8,000 women across the U.S. and Canada. The study tested the effectiveness of Simplirix™, a herpes simplex virus (HSV) vaccine developed by GlaxoSmithKline (GSK), in preventing genital herpes lesions in females ages 18-30. In two smaller studies, the vaccine was ineffective with men but prevented genital herpes outbreaks in over 70% of women who were free of both HSV-1 and HSV-2.
Spurred by the vaccine’s success with women in these initial studies, researchers from GSK and the National Institute of Allergy and Infectious Diseases (NIAID) collaborated on the larger Phase III trial in which subjects received either Simplirix™ or a hepatitis A vaccine (also manufactured by GSK). Participants were evaluated for both HSV infection by antibody studies and genital lesions over 20 months. Unlike the previous studies, however, the results were disappointing: In a press release, NIAID estimated the effectiveness of Simplirix™ in preventing HSV-related genital diseases was 20%, which researchers determined was not statistically significant. Following the NIAID announcement, GSK released a statement saying it would no longer pursue Simplirix™ research.
More data on the Herpevac for Women trial is slated to be discussed at the October meeting of the Infectious Diseases Society of America, and some experts caution the current results should be regarded as preliminary until more details are reported. Edward M. Hook, III, M.D., director of the Division of Infectious Diseases in the Department of Medicine at the University of Alabama, Birmingham, said this news won’t deter scientists working on HSV vaccines: “This research involved [thousands of] participants and, as analyses progress, the study will provide a wealth of data on events around the acquisition of herpes infections. Further, it is important to realize that while all of the investigators had hoped that the vaccine would be successful, investigators will continue to work on efforts to prevent HSV infections through vaccination and the topic remains a priority of the National Institutes of Health.”
HSV infections are common, with the majority of adults in the U.S. believed to have HSV-1 (often in the form of oral herpes that causes cold sores). According to the Centers for Disease Control and Prevention (CDC), approximately 17% of adults in the U.S. have HSV-2, most often experienced as a genital infection.
Resources: ASHA’s Herpes Resource Center NIAID press release GSK statement Read the NIAID press release. The GSK statement is online as well. For more on genital herpes, visit ASHA’s Herpes Resource Center.