#Correspondence
Fachun Jiang, Dr: Qingdao Municipal Center for Disease Control and Prevention, Qingdao Institute of Prevention Medicine, Qingdao City, Shandong Province, P.R.China. No.175 Shandong Road, 266033, China. E-mail: 13583206500@163.com
Zhaoguo Wang, Dr: Qingdao Municipal Center for Disease Control and Prevention, Qingdao Institute of Prevention Medicine, Qingdao City, Shandong Province, P.R.China. No.175 Shandong Road, 266033, China. E-mail: 470421859@qq.com
Ruqin Gao, MM: Qingdao Municipal Center for Disease Control and Prevention, Qingdao Institute of Prevention Medicine, Qingdao City, Shandong Province, P.R.China. No.175 Shandong Road, 266033, China. E-mail: ruqingao123@sina.com
Wei Ni, MM: Qingdao Women and Children’s Hospital, Qingdao University, Qingdao, Shandong Province, P.R.China, No.6 Tongfu Road, 266000, Qingdao, China. E-mail: 115438779@qq.com