Funding for this research was provided by:
Bill and Melinda Gates Foundation (OPP1139859)
Received: 10 December 2019
Accepted: 21 April 2020
First Online: 10 June 2020
Ethics approval and consent to participate
: The study only comprises of secondary analysis of published data and hence was not subject to ethical approval.
: Not applicable
: The authors declare that they have no competing interests.