In this trial, girls aged 10–14 years old were given three doses of an AS04-adjuvanted human papillomavirus (HPV)-16/18 L1 virus-like particle (VLP) vaccination. Girls who got three doses in the primary controlled, observer-blinded, randomised trial (NCT00196924) were invited to a 10-year follow-up. Using type-specific VLP as coating antigens, serum antibody responses against HPV-16/18 and HPV-31/45 were evaluated using an enzyme-linked immunosorbent assay (ELISA). Serious adverse events (SAEs) and pregnancy details were documented. All individuals were seropositive for anti-HPV-16/18 antibodies at Month (M) 120. In patients seronegative at baseline, geometric mean titers (GMTs) for anti-HPV-16 were 1589.9 ELISA Units [EU]/mL and 597.2 EU/mL for anti-HPV-18. Post-hoc mathematical modelling projected anti-HPV-16 and anti-HPV-18 durability of 50 years. All originally seronegative patients had seroconverted at M7 for the non-vaccine humoral type response, with anti-HPV-31 GMT of 2030.5 EU/mL and anti-HPV-45 GMT of 2300.8 EU/mL. At M120, 87.7 percent remained seropositive for anti-HPV-31 with a GMT of 242.9 EU/mL and 85.1 percent remained seropositive for anti-HPV-45 with a GMT of 204.7 EU/mL, respectively. Vaccination was not linked to any SAEs or adverse pregnancy outcomes throughout the 10-year follow-up.

During a 10-year follow-up, three doses of the AS04-HPV-16/18 vaccination elicited a strong and persistent antibody response against HPV-16,18,31, and 45 in girls aged 10–14 years, with an acceptable long-term safety profile.