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This observer-blind study (clinicaltrials.gov NCT01462357) compared the immunogenicity and safety of two doses (2D) of the HPV-16/18 AS04-adjuvanted vaccine (2D of AS04-HPV-16/18) vs. two or three doses of the 4vHPV vaccine [2D or 3D of 4vHPV] in 1075 healthy girls aged 9–14 years. Girls were randomized (1:1:1) to receive 2D of AS04-HPV-16/18 at months (M) 0, 6 (N = 359), 2D of 4vHPV at M0, 6 (N = 358) or 3D of 4vHPV at M0, 2, 6 (N = 358). 351, 339 and 346 girls, respectively, returned for the concluding visit at M36. Superiority was demonstrated at M7 and M12; comparison of the immune response to both vaccine antigens was made between 2D of AS04-HPV-16/18 and 2D or 3D of 4vHPV at subsequent time points in the according-to-protocol immunogenicity cohort (ATP-I; N = 958 at M36) and the total vaccinated cohort (TVC: N = 1036 at M36). HPV-16/18-specific T-cell- and B-cell-mediated immune responses and safety were also investigated. At M36, anti-HPV-16/18 ELISA responses in the 2D AS04-HPV-16/18 group remained superior to those of the 2D and 3D 4vHPV groups. In the M36 TVC, geometric mean titers were 2.78-fold (HPV-16) and 6.84-fold (HPV-18) higher for 2D of AS04-HPV-16/18 vs. 2D of 4vHPV and 2.3-fold (HPV-16) and 4.14-fold (HPV-18) higher vs. 3D of 4vHPV. Results were confirmed by vaccine pseudovirion-based neutralisation assay. Numbers of circulating CD4+ T cells and B cells appeared similar across groups. Safety was in line with the known safety profiles of both vaccines. In conclusion, superior HPV-16/18 antibody responses were elicited by 2D of the AS04-HPV-16/18 compared with 2D or 3D of the 4vHPV vaccine in girls aged 9–14 years. Clinical Trial Registration: NCT0146235 .

Summary Human papillomavirus vaccination began using a 3-dose schedule. Compared with the 3-dose schedule in women, the 2-dose schedules are effective options in young girls as of 36 months after first dose. Two-dose schedules could improve compliance and vaccination coverage., Background. We previously reported the noninferiority 1 month after the last dose of 2-dose human papillomavirus 16/18 AS04-adjuvanted (AS04-HPV-16/18) vaccine schedules at months 0 and 6 (2D_M0,6) and months 0 and 12 (2D_M0,12) in girls aged 9–14 years compared with a 3-dose schedule at months 0, 1, and 6 (3D_M0,1,6) in women aged 15–25 years. Here, we report the results at study end (month 36 [M36]). Methods. Girls were randomized 1:1 and received 2 vaccine doses either 6 months (2D_M0,6) or 12 months apart (2D_M0,12); women received 3 doses at months 0, 1, and 6 (3D_M0,1,6). Endpoints included noninferiority of HPV-16/18 antibodies for 2D_M0,6 versus 3D_M0,1,6; 2D_M0,12 versus 3D_M0,1,6; and 2D_M0,12 versus 2D_M0,6; and assessment of neutralizing antibodies, T cells, B cells, and safety. Results. At M36, the 2D_M0,6 and 2D_M0,12 schedules remained noninferior to the 3D_M0,1,6 schedule in terms of seroconversion rates and 3D/2D geometric mean titers for anti-HPV-16 and anti-HPV-18. All schedules elicited sustained immune responses up to M36. Conclusions. Both 2-dose schedules in young girls remained noninferior to the 3-dose schedule in women up to study conclusion at M36. The AS04-HPV-16/18 vaccine administered as a 2-dose schedule was immunogenic and well tolerated in young girls.

Persistent infection with a high-risk human papillomavirus (HPV) type is a prerequisite for cervical cancer [1–3]; therefore, prophylactic HPV vaccination is expected to substantially reduce the burden of this disease, particularly in countries without effective cervical screening programs. The licensed vaccines HPV-16/18 AS04-adjuvanted (Cervarix; GSK Vaccines) and HPV-6/11/16/18 (Gardasil; Merck & Co) were first approved as regimen including 3 doses (3D) with administration over a 6-month period. Reduced dose schedules could make vaccination easier to implement and more affordable, creating the potential for higher vaccination coverage and improved cervical cancer protection [4]. Evaluation of schedules including 2 doses (2D) of the HPV vaccine for girls was first prompted by the observation that 3D schedules elicited HPV-16/18 antibody titers approximately 2-fold higher in girls than in young women [5, 6], the age group in which efficacy was demonstrated in clinical studies [7–13]. A preliminary immunogenicity study evaluating the HPV-16/18 AS04-adjuvanted vaccine showed that 2D given at months 0 and 6 to girls aged 9–14 years was immunologically noninferior 1 month after the last dose to 3D given at months 0, 1, and 6 (M0,1,6) to women aged 15–25 years, and that antibody titers were sustained at high levels for up to 5 years [14–16]. However, the preliminary study was not powered to formally compare immunogenicity between groups beyond 1 month after the last dose. Therefore, the current large phase III study was designed to formally evaluate noninferiority and safety of 2 alternative 2D schedules (months 0 and 6 [M0,6] and months 0 and 12 [M0,12]) in girls aged 9–14 years compared with 3D in women aged 15–25 years over a 3-year period. The study is ongoing, and here we report data up to month 12 or month 13 (depending on the group).

This observer-blind study (clinicaltrials.gov NCT01462357) compared the immunogenicity and safety of 2 doses of the HPV-16/18 AS04-adjuvanted vaccine (HPV-16/18(2D)) vs. 2 or 3 doses of the HPV-6/11/16/18 vaccine (HPV-6/11/16/18(2D) and HPV-6/11/16/18(3D)) in healthy girls aged 9-14 y. Girls were randomized (1:1:1) to receive HPV-16/18(2D) at months (M) 0,6 (N = 359), HPV-6/11/16/18(2D) at M0,6 (N = 358) or HPV-6/11/16/18(3D) at M0,2,6 (N = 358). The primary objective was non-inferiority/superiority of HPV-16/18 antibodies by ELISA for HPV-16/18(2D) vs. HPV-6/11/16/18(2D) at M7 in the according-to-protocol immunogenicity cohort (ATP-I) and total vaccinated cohort, respectively. Secondary objectives included non-inferiority/superiority of HPV-16/18(2D) vs. HPV-6/11/16/18(3D) at M7, non-inferiority/superiority at M12, HPV-16/18 neutralizing antibodies, frequencies of T-cells/B-cells, reactogenicity and safety. Antibody responses at M7 for HPV-16/18(2D) were superior to those for HPV-6/11/16/18(2D) and HPV-6/11/16/18(3D) (lower limit of 95% confidence interval for geometric mean titer ratio (GMR) was >1): HPV-16/18(2D)/HPV-6/11/16/18(2D) GMRs were 1.69 [1.49-1.91] for anti-HPV-16 and 4.52 [3.97-5.13] for anti-HPV-18; HPV-16/18(2D)/HPV-6/11/16/18(3D) GMRs were 1.72 [1.54-1.93] for anti-HPV-16 and 3.22 [2.82-3.68] for anti-HPV-18; p = 0.0001 for all comparisons. Non-inferiority/superiority was also demonstrated at M12. Among initially seronegative girls in the ATP-I, neutralizing antibody titers were at least 1.8-fold higher for HPV-16/18(2D) vs. HPV-6/11/16/18(2D) and HPV-6/11/16/18(3D) at M7 and M12. Frequencies of HPV-16/18-specific T-cells and B-cells were in similar ranges between groups. Reactogenicity and safety were in line with the known profile of each vaccine. In conclusion, superior HPV-16/18 antibody responses were elicited by 2 doses of the HPV-16/18 AS04-adjuvanted vaccine compared with 2 or 3 doses of the HPV-6/11/16/18 vaccine in girls (9-14years). Funding: GlaxoSmithKline Biologicals SA