Funding for this research was provided by:
Bill and Melinda Gates Foundation
Received: 20 March 2017
Accepted: 30 January 2018
First Online: 12 March 2018
Ethics approval and consent to participate
: Ethical approval for the study was submitted to the Population Council’s Institutional Review Board, which exempted the project from review as it did not involve any primary data collection.
: Not applicable.
: The authors declare that they have no competing interests.
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