Funding for this research was provided by:
Bill and Melinda Gates Foundation (OPP1160129)
Received: 6 January 2020
Accepted: 6 March 2020
First Online: 30 March 2020
Ethics approval and consent to participate
: No ethics approval was sought for the writing of this paper.
: All authors provided consent for the publication of this paper.
: All authors state no competing interests.