Funding for this research was provided by:
Bill and Melinda Gates Foundation
Text and Data Mining valid from 2020-02-05
Received: 27 June 2019
Accepted: 9 January 2020
First Online: 5 February 2020
Ethics approval and consent to participate
: The study followed the guidelines of the Helsinki Declaration and was approved by the Ethics Committees of the Chinese Center for Disease Control and Prevention and the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences. All participants agreed to participate in the study and provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.