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.