The efficacy of the 9vHPV vaccine, developed to prevent HPV infection and disease caused by HPV6/11/16/18/31/33/45/52/58, was demonstrated in a Phase III study (Study 001) in young women (aged 16 to 26 years). In another Phase III study (Study 002), the efficacy results were bridged to girls and boys (aged 9-15 years) based on the demonstration of non-inferior HPV antibody responses compared to young women. Study 002 was extended to evaluate vaccine immunogenicity, efficacy and safety over 10 years. An interim analysis of immunogenicity of Study 002 up to 3 years and plans for longer term immunogenicity and effectiveness follow up will be presented.
Young women aged 16-26 years (Study 001) and girls and boys aged 9-15 years (Study 002) received 3 doses of 9vHPV vaccine at day1, month 2 and month 6. Serology was assessed at month 7, 12, 24, 36, using HPV-9 cLIA. Vaccine immunogenicity is estimated in the per-protocol population by assessing geometric mean titers (GMTs) and seropositivity rates to each vaccine type HPV. Non-overlapping 95% confidence intervals were used as indicators of differences of immune response
In Study 002, seropositivity rates to each of the 9 HPV types in girls and boys ranged from 99.9%to 100% at month 7 and from 93.8% to 99.7% at month 36. GMTs peaked at month 7, and decreased thereafter to plateau between month 24 and month 36. An analysis by age strata (9-12 years and 13-15 years at enrollment) showed that the month 36 seropositivity rates ranged from 96.5% to 99.7% in the younger group and 87.2% to 99.7% in the older group. This difference in GMTs by age strata was statistically significant in girls at all-time points; differences in boys were smaller and were not statistically significant.
Efficacy of the 9vHPV vaccine was established through 6 years of follow-up (median 4 years) in young women in Study 001. A cross-study comparison showed that GMTs in girls and boys from Study 002 were higher than GMTs in young women from Study 001 at month 7, and remained higher throughout the study. Based on these results, efficacy in girls and boys through month 36 is inferred. Study 002 was extended to continue assessment of antibody persistence and initiate assessment of effectiveness ( through 10 years post vaccination.
Administration of the 9vHPV vaccine in girls and boys aged 9-15 years resulted in HPV antibody responses that persisted through 3 years. HPV antibody responses remained higher in girls and boys than in young women (the population used to establish 9vHPV vaccine efficacy) for this entire study period. Longer term assessment of immunogenicity and effectiveness is ongoing.