Funding for this research was provided by:
Bill and Melinda Gates Foundation (OPP1134345)
Received: 13 June 2019
Accepted: 21 October 2019
First Online: 4 November 2019
Ethics approval and consent to participate
: As all of the data were retrieved from the freely-accessed official domains, therefore ethics approval is not required. Yet we had strictly followed the confidential requirement; all individual information was strictly kept confidential and was not reported in this paper.
: Not applicable.
: The authors declare that they have no competing interests.