Funding for this research was provided by:
Bill and Melinda Gates Foundation (Pilgrim 2016)
Text and Data Mining valid from 2019-08-09
Received: 29 April 2019
Accepted: 2 August 2019
First Online: 9 August 2019
Ethics approval and consent to participate
: This is already included in the text.
: This is not applicable as this manuscript uses aggregated data.
: The authors declare that they have no competing interests.