Vaccine for the Prevention of Genital Herpes Shows Promise

(22 Jan 2003)

According to the results of two late-stage trials, a vaccine derived from the glycoprotein-D of herpes simplex virus type 2 (HSV-2), the virus that commonly causes genital herpes, has shown efficacy against genital herpes in women but has no effect in men.

The HSV-2 vaccine is classed as a subunit vaccine as it is based on the glycoprotein-D-component of the herpes simplex virus type 2 rather than the whole virus, which makes it safe and stable. The effectiveness of the vaccine in the prevention of genital herpes infection was evaluated in two separate trials. Individuals were eligible for inclusion into one of the studies if their regular sexual partner had a history of genital herpes.

In the first study, participants' blood serum tested negative (seronegative) for both HSV-1, the most type of herpes simplex virus that usually causes facial herpes, and HSV-2. In the second study, participants could be either positive or negative to HSV-1. Participants were given either vaccine or a control injection at months 0, 1 and 6, and were tested for genital herpes disease for 19 months.

The vaccine was well tolerated and elicited both antibody and cellular responses. Overall vaccine efficacy was 38 and 42% in Study 1 and Study 2, respectively. Further analysis of the data from both studies showed that the vaccine was about 73% effective in preventing clinical disease in women who were seronegative for both HSV types, but had no effect in women who were already seropositive for HSV-1 at enrolment or in men.

The authors conclude: 'These studies suggest that the glycoprotein-D vaccine has efficacy against genital herpes in women who are seronegative for both HSV-1 and HSV-2 at baseline but not in those who are seropositive for HSV-1 and seronegative for HSV-2. It had no efficacy in men, regardless of their HSV serologic status'.

The study was published in the October 2002 edition of the New England Journal of Medicine. A large, phase III clinical trial is being initiated by GlaxoSmithKline Biologicals in partnership with the NIH (National Institute of Health - USA) to further investigate the safety and efficacy of this vaccine.

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