Randomized Open Trial Comparing 2-Dose Regimens of the Human Papillomavirus 16/18 AS04-Adjuvanted Vaccine in Girls Aged 9–14 Years Versus a 3-Dose Regimen in Women Aged 15–25 Years

BACKGROUND This randomized, open trial compared regimens including 2 doses (2D) of human papillomavirus (HPV) 16/18 AS04-adjuvanted vaccine in girls aged 9-14 years with one including 3 doses (3D) in women aged 15-25 years. METHODS Girls aged 9-14 years were randomized to receive 2D at months 0 and 6 (M0,6; (n = 550) or months 0 and 12 (M0,12; n = 415), and women aged 15-25 years received 3D at months 0, 1, and 6 (n = 482). End points included noninferiority of HPV-16/18 antibodies by enzyme-linked immunosorbent assay for 2D (M0,6) versus 3D (primary), 2D (M0,12) versus 3D, and 2D (M0,6) versus 2D (M0,12); neutralizing antibodies; cell-mediated immunity; reactogenicity; and safety. Limits of noninferiority were predefined as <5% difference in seroconversion rate and <2-fold difference in geometric mean antibody titer ratio. RESULTS One month after the last dose, both 2D regimens in girls aged 9-14 years were noninferior to 3D in women aged 15-25 years and 2D (M0,12) was noninferior to 2D (M0,6). Geometric mean antibody titer ratios (3D/2D) for HPV-16 and HPV-18 were 1.09 (95% confidence interval, .97-1.22) and 0.85 (.76-.95) for 2D (M0,6) versus 3D and 0.89 (.79-1.01) and 0.75 (.67-.85) for 2D (M0,12) versus 3D. The safety profile was clinically acceptable in all groups. CONCLUSIONS The 2D regimens for the HPV-16/18 AS04-adjuvanted vaccine in girls aged 9-14 years (M0,6 or M0,12) elicited HPV-16/18 immune responses that were noninferior to 3D in women aged 15-25 years. CLINICAL TRIALS REGISTRATION NCT01381575.