Antibody responses among adolescent females receiving two or three quadrivalent human papillomavirus vaccine doses at standard and prolonged intervals.

•Antibody responses in 9–17 year old girls enrolled from community settings were assessed.•GMTs after prolonged intervals were non-inferior to recommended intervals.•Six-month post-dose 3 GMTs after prolonged intervals were superior to recommended intervals.•A prolonged interval between dose 1 and 2 may enhance antibody response.•Antibody responses after delayed dose 2 were similar in older and younger girls.