1. Department of Epidemiology and Health Statistics, School of Public Health, Shaanxi University of Chinese Medicine, Xi'an, Shaanxi 712046, P.R. China
2. Department of Nursing, Health Science Center, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
3. Immunization Department of Center for Disease Control and Prevention of Xianyang, Xianyang, Shaanxi 712046, P.R. China
4. Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
5. Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
6. GoDaddy Inc, Sunnyvale, CA 95131, USA