1. Teaching Center for Preventive Medicine, School of Public Health, Anhui Medical University, Hefei, China
2. Department of Epidemiology and Health Statistics, School of Public Health, Anhui Medical University, Hefei, China
3. Department of Expanded Program on Immunization, Lu’an Municipal Center for Disease Control and Prevention, Lu’an, China
4. Department of Infectious Disease Control, Yu’an District Center for Disease Control and Prevention, Lu’an, China