To compare HPV-antibody responses in girls and boys aged 9-14 years given 2 doses of the 9vHPV vaccine versus women aged 16-26 years given 3 doses.
Protocol V503-010 is an international immunogenicity study of the 9vHPV vaccine using 5 cohorts: (1) girls receiving 2 doses 6-months apart; (2) boys receiving 2 doses 6-months apart; (3) girls and boys receiving 2 doses 12-months apart; (4-control): young women receiving 3 doses (D1, M2, M6); (5-exploratory) girls receiving 3 doses (D1, M2, M6). HPV-type specific geometric mean titers (GMTs) were assessed 1 month post-last dose by competitive Luminex immunoassay. Primary objectives were to demonstrate non-inferior HPV GMTs 1 month post-last dose in cohorts 1, 2, and 3 compared to cohort 4. Statistical criterion for non-inferiority required the lower bound of the 95% confidence interval of GMT ratios (cohort 1, 2, or 3/cohort 4) each be >0.67 for all HPV types.
GMTs for all 9 HPV types were non-inferior in girls and boys aged 9-14 years given 2 doses versus women aged 16-26 years given 3 doses (cohort 4). The primary objectives of non-inferior immunogenicity of 2-doses versus 3-doses were met. Most subjects seroconverted to all vaccine types. In girls aged 9-14 years, 2 doses elicited lower GMTs than 3 doses for some vaccine types.
Using these results, efficacy findings in young women given 3 doses of 9vHPV vaccine can be extrapolated to girls and boys 9-14 years old given 2 doses at 0, 6 or 0, 12 months.