The GARDASIL™ long-term follow-up (LTFU) study is an ongoing extension of a pivotal study (Protocol 015) to investigate the safety, immunogenicity, and effectiveness of GARDASIL™ on the incidence of HPV 16/18-related CIN2 or worse in 16-23-year old women. Here, we analyze the effectiveness and immunogenicity of the vaccine in this population of women up to 10-12 years after the start of vaccination.
All women in the trial are followed through different national registries (Denmark, Iceland, Norway and Sweden) for immunogenicity and effectiveness and safety data. Interim effectiveness and safety analyses started approximately 2 years following completion of Protocol 015 and have been occuring every 2 years thereafter. Cohort 1 included approximately 2,700 subjects who received GARDASIL™ at the start of Protocol 015. Cohort 2 consists of approximately 2,100 subjects who received placebo at the start of Protocol 015 and GARDASIL™ prior to entry into the LTFU. Vaccine effectiveness against HPV 16/18-related CIN2 or worse (CIN2+) was estimated by comparing the observed incidence with the expected incidence of CIN2+ in an unvaccinated cohort using historical registry data. This is the last interim analysis before the completion of the study (with 14 years of follow-up of the subjects in Cohort 1.)
In the analysis of effectiveness after the first 12 years, there were 2,084 subjects that contributed to the follow-up period out of a total of 2,650 eligible subjects in the per-protocol population in Cohort 1. No new cases of HPV 16/18-related CIN 2 or worse observed. There were also no cases of HPV 6/11/16/18-related CIN, vulvar cancer, and vaginal cancer observed.
GARDASIL™ shows continued protection in women through 10 years, with a trend towards 12 years of protection.