Funding for this research was provided by:
the National Key Research and Development Program of China (2016YFC0900500, 2016YFC0900501, 2016YFC0900504,)
Kadoorie Charitable Foundation (088158/Z/09/Z, 104085/Z/14/Z, 104085/Z/14/Z)
Received: 8 November 2019
Accepted: 18 May 2020
First Online: 29 May 2020
Ethics approval and consent to participate
: The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008.This study has been approved by the Institutional Review Boards at Oxford University and the China National Center for Disease Control.All the participants included in this study provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.