Safety and Immunogenicity of a 9-Valent Human Papillomavirus Vaccine Administered to 9- to 15-Year-Old Japanese Girls.

A 9-valent human papillomavirus (HPV 6/11/16/18/31/33/45/52/58) virus-like particle vaccine (9vHPV) has been proven highly efficacious in preventing anogenital diseases related to HPV, in a pivotal phase III study for women aged 16-26 years. Here, we report the results of an open-label phase III study conducted to bridge the gap between the findings in women aged 16-26 years and Japanese girls aged 9-15 years. All subjects (n = 100) received a 3-dose regimen of 9vHPV vaccine on day 1 and at months 2 and 6. Anti-HPV serological assays were performed on day 1 and at months 7, 12, 24, and 30. At month 7 (4 weeks after the third dose), 100% of the subjects exhibited seroconversion for each type of HPV. Increases in geometric mean of the titers for anti-HPV 6/11/16/18/31/33/45/52/58 in the subjects were similar to those in Japanese women aged 16-26 years in a previous phase III study. Persistence of the anti-HPV response was observed for 2 years after administration of the third dose. In addition, administration of the 9vHPV vaccine was generally well-tolerated in Japanese girls.