Long-Term Immune Persistence After Bivalent HPV Vaccination in Females From Study 311-HPV-1005

This is a single-center, open-label, prospective observational extension of Study 311-HPV-1005 (NCT04965350). The study follows females who received at least one dose of a bivalent human papillomavirus vaccine containing HPV-16 and HPV-18 L1 virus-like particles in the base study. No vaccine is administered in this extension. Participants in the immunogenicity persistence subset provide blood samples at Months 42 and 66 after the first dose in the base study for measurement of HPV-16 and HPV-18 neutralizing antibodies. Participants eligible for the breakthrough-case cohort are followed for HPV-related cervical disease, including HPV-16- or HPV-18-related cervical intraepithelial neoplasia grade 2 or worse.