Background: Vaccine efficacy (VE) against vulvar human papillomavirus (HPV) infection has not been reported and data regarding its epidemiology are sparse.
Methods: Women (n = 5404) age 22-29 present at the 4-year study visit of the Costa Rica Vaccine Trial provided vulvar and cervical samples. A subset (n = 1044) was tested for HPV DNA (SPF10/LiPA25 version 1). VE against 1-time detection of vulvar HPV16/18 among HPV vaccinated versus unvaccinated women was calculated and compared to the cervix. Prevalence of and risk factors for HPV were evaluated in the control arm (n = 536).
Results: Vulvar HPV16/18 VE (54.1%; 95% confidence interval [CI], 4.9%-79.1%) was comparable to cervix (45.8%; 95% CI, 6.4%-69.4%). Vulvar and cervical HPV16 prevalence within the control arm was 3.0% and 4.7%, respectively. Independent risk factors for vulvar HPV were similar to cervix and included: age (adjusted odds ratio [aOR] 0.5 [95% CI, .3-.9] ≥28 vs 22-23]); marital status (aOR 2.3 [95% CI, 1.5-3.5] single vs married/living-as-married); and number of sexual partners (aOR 3.6 [95% CI, 1.9-7.0] ≥6 vs 1).
Conclusions: In this intention-to-treat analysis, VE against vulvar and cervical HPV16/18 were comparable 4 years following vaccination. Risk factors for HPV were similar by anatomic site.
Clinical trials registration: NCT00128661.
Keywords: Costa Rica; HPV; HPV vaccine; vulvar human papillomavirus vaccine.
Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.