Funding for this research was provided by:
Bill & Melinda Gates Foundation (OPP1160129)
Received: 14 April 2019
Accepted: 9 July 2019
First Online: 17 July 2019
Ethics approval and consent to participate
: The research protocol was reviewed and approved by the Human Research Protection Program Institutional Review Board (IRB) of the University of California San Francisco (17-22884).
: Not applicable.
: The authors declare that they have no competing interests.