Funding for this research was provided by:
Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by Korean government MSIP (No. 2016M3A9B694241)
National Research Foundation of Korea (NRF) grant funded by the Korea government (NRF-2017R1C1B5018142)
Received: 9 October 2017
Accepted: 11 October 2018
First Online: 20 October 2018
Ethics approval and consent to participate
: The Korea Centers for Disease Control and Prevention (KCDC) Institutional Review Board approved the survey protocol, and all participants provided written informed consent (approval nos. 2010-02CON-21C, 2011-02CON-06-C, and 2012-01EXP-01-2C).
: Not applicable.
: The authors declare that they have no competing interests.
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