Zhang, Jingfeng
Han, Xinxin
Yang, Zhenghan
Wang, Zhenchang
Zheng, Jianjun
Yang, Zimo
Zhu, Jiming
Article History
Received: 8 December 2020
Accepted: 19 January 2021
First Online: 17 February 2021
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board at Research Center for Public Health, Tsinghua University. Informed consents were obtained from all participants. Participation in the study was voluntary, and participants were assured that there would be no negative consequences on anyone who did not wish to participate in the study or who decided to withdraw after giving consent.
: Not applicable.
: The authors declare that they have no competing interests.