Although previous studies of a new genital herpes vaccine were encouraging, it failed to protect women in a recent large clinical trial.
Dr. Robert B. Belshe, director of the division of infectious disease and immunology at Saint Louis University, and colleagues looked at efficacy data for an investigational vaccine for the herpes simplex virus. The randomized, double-blind efficacy field trial included 8,323 women aged 18 to 30 years who were negative for antibodies to herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). Participants either received the investigational vaccine, which consisted of 20 μg of glycoprotein D from HSV-2 with alum and 3-O-deacylated monophosphoryl lipid A as an adjuvant, or the control agent, which consisted of the hepatitis A vaccine, at study initiation and again at month 1 and month 6. The women were followed for 20 months and were monitored for HSV-1 or HSV-2 from month two onward.
Belshe and colleagues did not find the vaccine to be efficacious and noted the vaccine was associated with negative effects. Belshe and colleagues determined that the overall vaccine efficacy was 20% against genital herpes disease. For HSV-1 infection specifically, the vaccine efficacy was slighter higher (35%). However, the vaccine seemed to fail completely against HSV-2 infection. Moreover, in comparison with the control vaccine, the investigational vaccine was associated with an increased risk of local reactions. The investigational vaccine also elicited enzyme-linked immunosorbent assay (ELISA) and neutralizing antibodies to HSV-2.
Based on these findings, the authors noted that while the investigational vaccine holds promise, it will not yet protect the general population against genital herpes. Previous studies found a 73% and 74% efficacy against genital disease in women who were negative for both HSV-1 and HSV-2 antibodies. In those studies, the vaccine was not deemed efficacious in men or women who were HSV-1 seropositive.
Belshe and colleagues concluded, “In a study population that was representative of the general population of HSV-1– and HSV-2–seronegative women, the investigational vaccine was effective in preventing HSV-1 genital disease and infection but not in preventing HSV-2 disease or infection.”
Belshe RB, Leone PA, Bernstein DI, et al. Efficacy results of a trial of a herpes simplex vaccine. N Engl J Med. 2012;366:34-43.