2Department of Microbiology, Linyi Center for Disease Control and Prevention, Linyi, China
3Department of Immunology, School of Basic Medicine, Qingdao University, Qingdao, China
4Department of Infectious Disease, The Affiliated Hospital of Qingdao University, Qingdao, China
5Department of Medical Education, Qingdao Chest Hospital, Qingdao, China
6Department of Infectious Disease, Qingdao Centre for Disease Control and Prevention, Qingdao Institute of Prevention Medicine, Qingdao, China
7Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, Qingdao, China
Although vaccine resources are being distributed worldwide, insufficient vaccine production remains a major obstacle to herd immunity. In such an environment, the cases of re-positive occurred frequently, and there is a big controversy regarding the cause of re-positive episodes and the infectivity of re-positive cases. In this case-control study, we tracked 39 patients diagnosed with COVID-19 fr