Funding for this research was provided by:
Bill and Melinda Gates Foundation
the German Federal Ministry for Economic Cooperation and Development
Text and Data Mining valid from 2019-08-13
Received: 6 June 2018
Accepted: 25 July 2019
First Online: 13 August 2019
Ethics approval and consent to participate
: Not applicable.
: All authors read and approved the final manuscript.
: The authors declare that they have no competing interests.