Funding for this research was provided by:
Bill and Melinda Gates Foundation (OPP1164115)
Received: 26 June 2018
Accepted: 10 July 2019
First Online: 18 July 2019
Ethics approval and consent to participate
: Ethical approval was obtained from the University of the Witwatersrand Committee for Research on Human Subjects (approval ID #M010556). Written participant assent and caregiver permission to participate in the study were obtained at each wave.
: Not applicable.
: The authors declare that they have no competing interests.