Longer term efficacy of a prophylactic monovalent human papillomavirus type 16 vaccine

Abstract

We conducted an extended follow-up study (March 2006–May 2008) to assess the longer term efficacy of a prophylactic monovalent human papillomavirus (HPV) type 16 L1 virus-like particle vaccine in women ( n = 290) who had enrolled in a randomized controlled trial of this vaccine (October 1998–November 1999) in Seattle and remained HPV-16 DNA negative during the course of that trial. During the extended follow-up period, in the per-protocol susceptible population, none of the vaccine recipients was found to be infected with HPV-16 or developed HPV-16-related cervical lesions; among placebo recipients, 6 women were found to be infected with HPV-16 (vaccine efficacy [VE] = 100%; 95% confidence interval [CI]: 29–100%) and 3 women developed HPV-16-related cervical lesions (VE = 100%; 95% CI: <0–100%). Approximately 86% of vaccine recipients remained HPV-16 competitive Luminex immunoassay seropositive at an average of 8.5 years of follow-up. During the combined original trial and extended follow-up period, in the intention-to-treat population, 20 and 22 women developed any cervical lesion regardless of HPV type among the vaccine and placebo recipients, respectively (VE = 15%; 95% CI: <0–56%). The results suggest that this monovalent HPV-16 vaccine remains efficacious through 8.5 years after its administration.