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CDC HIV/AIDS/Viral Hepatitis/STD/TB Prevention News Update
Recombinant Glycoprotein Vaccine for the Prevention of Genital
Corey, Lawrence; Langenberg, Andria G.M.; Ashley, Rhoda; et
July 28, 1999
Journal of the American Medical Association (07/28/99) Vol.

Investigators for the Chiron HSV Vaccine Study Group found that protection from herpes simplex virus type 2 (HSV-2) will require vaccines to do more than induce high levels of specific neutralizing antibodies. The researchers conducted two randomized, double-blind, placebo-controlled multicenter trials of a recombinant subunit vaccine against the virus. The vaccine contained gB2 and gD2, HSV-2 surface proteins against which neutralizing antibodies are directed. Subjects were vaccinated at months 0, 1, and 6. Participants in the control group received a citrate buffer vehicle, and all subjects were followed up after the third immunization. Researchers measured outcome by time to acquisition of HSV-2. During the first five months of the trial, those receiving the vaccine had a 50 percent lower acquisition rate than the controls. According to the data, the acquisition rate of HSV- 2 for vaccinated subjects was 4.6 per 100 patient years, compared to 4.2 per 100 patients years in those receiving the placebo. Although the vaccine induced high levels of HSV-2 specific neutralizing antibodies in all subjects, follow-up study revealed that the vaccine had no significant influence on duration of clinical first episodes of genital HSV-2 or frequency of reactivation. Furthermore, overall vaccine efficacy was 9 percent. The researchers assert that an effective vaccine must have a higher efficacy level than 9 percent and should do more than stimulate high levels of specific neutralizing antibodies.