An outbreak of type π vaccine-derived poliovirus in Sichuan province, China: emergence and circulation in an under-immunized population. oleh Hai-Bo Wang, Gang Fang, Wen-Zhou Yu, Fei Du, Chun-Xiang Fan, Qing-Lian Liu, Li-Xin Hao, Yu Liu, Jing-Shan Zheng, Zhi-Ying Qin, Wei Xia, Shi-Yue Zhang, Zun-Dong Yin, Qiong Jing, Yan-Xia Zhang, Rong-Na Huang, Ru-Pei Yang, Wen-Bin Tong, Qi Qi, Xu-Jing Guan, Yu-Lin Jing, Qian-Li Ma, Jin Wang, Xiao-Zhen Ma, Na Chen, Hong-Ru Zheng, Yin-Qiao Li, Chao Ma, Qi-Ru Su, Kathleen H Reilly, Hui-Ming Luo, Xian-Ping Wu, Ning Wen, Wei-Zhong Yang