Long-term Immune Persistence of a Bivalent HPV Vaccine in Females From Study 311-HPV-1004

This long-term extension study evaluates the persistence of neutralizing antibody responses to a bivalent human papillomavirus vaccine in females who previously participated in study 311-HPV-1004 (NCT02740777). Participants belonged to one of three vaccination cohorts in the base study: adolescents who received two doses at Months 0 and 6, adolescents who received three doses at Months 0, 2, and 6, and adults who received three doses at Months 0, 2, and 6. No vaccine is administered in the extension study. Blood samples are collected at Months 84, 108, and 132 after the first dose in the base study and tested for HPV-16 and HPV-18 neutralizing antibodies using a high-throughput pseudovirus-based neutralization assay.