The effectiveness of pay-it-forward in addressing HPV vaccine delay and increasing uptake among 15–18-year-old adolescent girls compared to user-paid vaccination: a study protocol for a two-arm randomized controlled trial in China

• Yifan LiSichuan University
• Chuanyu QinSichuan University
• Shengyue QiuSichuan University
• Yu HeSichuan University
• Linchuan Pang
• Xiaolan Xu
• Vivian Wan-Cheong YimTuen Mun Hospital
• Shenglan TangDuke University
• Heng DuGates Foundation
• Wenfeng GongGates Foundation
• Fan YangPeking University
• Joseph D. TuckerUniversity of North Carolina at Chapel Hill
• Weiming TangUniversity of North Carolina at Chapel Hill
• Yun WangChapman University
• Leesa K. LinLondon School of Hygiene & Tropical Medicine
• Mark JitLondon School of Hygiene & Tropical Medicine
• Wei SongHealth Commission of Chengdu Municipality
• Chunrong LiUniversity of Electronic Science and Technology of China
• Jennifer L. SmithUniversity of North Carolina at Chapel Hill
• Jing LiSichuan University
• Dan WuLondon School of Hygiene & Tropical Medicine