Vaccine efficacy against vulvar infection with HPV 16/18 was comparable to the efficacy found against cervical infection 4 years after vaccination, according to researchers with the National Cancer Institute.
“Findings presented here and in the literature suggest that the incidence of HPV infection and resultant cancers will decrease at several anatomic sites in women who receive the prophylactic HPV vaccines before exposure to the virus,” the researchers wrote in The Journal of Infectious Diseases. “Unfortunately, among unvaccinated women, vulvar HPV infection will remain common.”
This study was a nested analysis within the Costa Rica Vaccine Trial, in which women aged 18 to 25 years were randomly assigned to bivalent HPV 16/18 vaccine (Cervarix, GlaxoSmithKline) or a control hepatitis A vaccine to assess the vaccine efficacy against cervical infection. At the 4-year study visit, sexually experienced women were asked to provide vulvar, cervical and anal specimens for testing. The intention-to-treat cohort for this study included all women who provided vulvar specimens and had HPV results available.
Among the 5,404 women who provided vulvar samples, 1,044 were tested for HPV: 508 in the vaccine arm and 536 in the control arm. Vulvar vaccine efficacy was 54.1% (95% CI, 4.9-79.1), with 10 events in the vaccine arm and 23 in the control arm. The cervical vaccine efficacy was 45.8% (95% CI, 6.4-69.4), with 19 events in the vaccine arm and 37 in the control arm.
The overall prevalence of any HPV in the vulva was 29.5% (95% CI, 25.6-33.5). The prevalence of carcinogenic HPV types was 16.8% (95% CI, 13.7-20.2), the most common being HPV 52 (3.4%), HPV 56 (3.4%) and HPV 16 (3%). Independent risk factors for vulvar HPV infection included age, marital status and number of sexual partners.
“Based on the cumulative work to date in our trial, we now understand the HPV vaccine protects against HPV infections at all anatomic sites where HPV causes cancer, including the cervix, vulva, anus and oral region,” the researchers wrote.
Disclosure: GlaxoSmithKline provided the vaccine and additional support for the trial.