1. Department of Epidemiology and Health Statistics, West China School of Public Health and West China Fourth Hospital, Sichuan University, Sichuan, People’s Republic of China
2. Public Health Clinical Center of Chengdu, Sichuan, People’s Republic of China
3. Department of Immunization Program, Chengdu Municipal Center for Disease Control and Prevention, Sichuan, People’s Republic of China
4. Department of Microbiology Laboratory, Chengdu Municipal Center for Disease Control and Prevention, Sichuan, People’s Republic of China