Received: 15 May 2022
Accepted: 26 October 2022
First Online: 3 November 2022
: This research protocol was approved by the Ethics Committee of Chinese Center for Disease Control and Prevention (Beijing, China) to commencing the study in accordance with relevant guidelines and regulations. Each questionnaire had attached an informative letter at first, which clarified the free participation, anonymity, and confidentiality of this study. Participants were informed on the research and signed an informed consent form.
: Not applicable.
: The authors declare that they have no competing interests.