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Study Shows New Herpes Vaccine is Safe and Provides Good Immune Response

ORLANDO, Fla., Oct. 7, 1994 -- A new herpes virus vaccine in development by SmithKline Beecham showed rapid onset and good persistence of immune response in a recently completed Phase II clinical trial. The study was presented on October 7, 1994 at the 34th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

Forty subjects (seronegative) who were not infected with either herpes simplex virus (HSV) type 1 (the virus which primarily causes cold sores) or HSV type 2 (the virus which primarily causes genital herpes), demonstrated positive antibody response to vaccine antigen following vaccination, and more importantly, demonstrated a strong cellular response.

"A persistent cellular immune response may be the key to preventing initial clinical herpes virus disease and reducing the severity and frequency of recurrences in patients with pre-existing clinical genital herpes disease," said Dr. Moncef Slaoui, director of immunology, SmithKline Beecham Biologicals, Belgium. "This study confirms earlier results in animals."

Eighty volunteers, aged 19 to 40 years of age, half seronegative and half seropositive, participated in a prospective, double-blind study. They were equally randomized into two groups--one group receiving an experimental vaccine formulation with an immunostimulant, monophosphoryl lipid A (MPL*); the other group, a formulation without MPL.

"All of these individuals demonstrated antibody responses, and the levels of antibodies following three doses were similar to those seen after natural infection with herpes viruses," Dr. Slaoui said. "However, the group receiving the vaccine with MPL showed consistently faster antibody response

and longer lasting cellular immune response--both in vivo and in vitro, than those receiving the vaccine without MPL."

"Responses were sustained up to the end of the study observation period of 13 months after the initial injection of the vaccine," Slaoui added. "The objective of the trial was to study safety of the vaccines in both seropositive and seronegative individuals in addition to the immune responses."

As with other vaccines, the most commonly reported side effect seen in volunteers was soreness at the injection site, which generally resolved within a few days. Slightly more reports were noted in the MPL vaccine group compared to the vaccine without MPL and in the seropositive individuals compared to the seronegative group. No serious vaccine-related adverse events were reported.

Genital herpes is a contagious viral infection that affects an estimated 55 million Americans and Europeans between the ages of 15 and 74. Each year an estimated 750,000 new cases are believed to occur. In the U.S. alone, up to 80 percent of patients with genital herpes suffer from symptomatic recurrences of the disease following an initial outbreak. Currently, there are no vaccines on the market for prevention or treatment of HSV, and there is no cure.

A Phase III study will begin in November to confirm protective efficacy in people at risk for acquiring genital herpes infection--people who do not have the disease but are at high risk because their steady sexual partner has active genital herpes disease. This study with the MPL vaccine formulation will include centers in the United States, the United Kingdom, Canada, Germany, Italy, Australia and New Zealand.

In addition, a study is underway with the MPL vaccine formulation for the treatment of patients with frequently recurring genital herpes disease at centers in Canada and Sweden.

Results of these Phase III studies will be available within the next 18 months.

The vaccine under development is a subunit vaccine which incorporates cloned herpes simplex virus glycoprotein expressed in mammalian cells.

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*MPL is licensed to SB from RIBI ImmunoChem, U.S.

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Posted: July 2004