Safety and Immunogenicity of the Quadrivalent HPV Vaccine in Japanese Boys: a Phase 3, Open-Label Study.

Human papillomavirus (HPV)-associated disease is common among men with HPV infection. A quadrivalent HPV (qHPV) vaccine has demonstrated 85.9% efficacy against HPV6/11/16/18-related, persistent (≥ 6 month) infection in a study of Japanese men aged 16-26 years old. Here, we report the results of an open-label study of the immunogenicity and tolerability of the qHPV vaccine (NCT02576054), conducted to bridge findings from Japanese men to Japanese boys aged 9-15 years old. A total of 100 boys completed a three-vaccination regimen (Day 1, and Months 2 and 6), and 99 boys were included in the primary analysis population. The rate of seroconversion at one month after vaccine Dose 3 (Month 7) was high for each type of HPV (anti-HPV6/11/16/18 seroconversion rates [95% CI]: 94.9% [85.5%, 98.3%], 99.0% [94.4%, 100.0%], 99.0% [94.5%, 100.0%], and 99.0% [94.4%, 100.0%], respectively). Moreover, anti-HPV6/11/16/18 geometric mean titers were 482.9 mMU/mL, 1052.8 mMU/mL, 3878.3 mMU/mL, and 1114.5 mMU/mL, respectively. Immune responses to the qHPV vaccine were non-inferior among Japanese boys included in the current study and compared with young Japanese men from a separate study. Injection-site reactions were the most common adverse events, and administration of the vaccine was well tolerated in Japanese boys.