Funding for this research was provided by:
Korea Centers for Disease Control and Prevention (2018P330400)
Received: 14 June 2020
Accepted: 19 November 2020
First Online: 25 November 2020
Ethics approval and consent to participate
: This study was approved by the Seoul National University Hospital Institutional Review Board (IRB number: E-1806-076-951). The requirement for informed consent was waived as the NHIS-NSC database was anonymized according to strict confidentiality guidelines prior to distribution.
: Not applicable.
: None of the authors have any conflicts to report.