Data and analysis code for Cai J, Yang J, Deng X, Peng C, Chen X, Wu Q, Wu Q, Liu H, Zhang J, Zheng W, Zou J, Zhao Z, Ajelli M, Yu H. (2022). Assessing the transition of COVID-19 burden towards the young population while vaccines are rolled out in China. Emerging Microbes & Infections, 1-52. doi:10.1080/22221751.2022.2063073.