Funding for this research was provided by:
Kadoorie Charitable Foundation
Wellcome Trust (202922/Z/16/Z, 104085/Z/14/Z, 088158/Z/09/Z)
National Natural Science Foundation of China (81390540, 81390541, 81390544)
Ministry of Science and Technology of the People's Republic of China (2016YFC 0900500, 0900501, 0900504, 1303904)
Text and Data Mining valid from 2019-02-20
Received: 27 November 2018
Accepted: 31 January 2019
First Online: 20 February 2019
Ethics approval and consent to participate
: Ethical approval was obtained from the Ethical Review Committee of the Chinese Centre for Disease Control and Prevention (Beijing, China) and the Oxford Tropical Research Ethics Committee, University of Oxford (UK), and all participants provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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