Funding for this research was provided by:
South African Medical Research Council
Wellcome Trust
DST/NRF Centre of Excellence at the University of the Witwatersrand
National Research Foundation
Article History
Received: 1 August 2018
Accepted: 9 April 2019
First Online: 2 May 2019
Ethics approval and consent to participate
: This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving human subjects were approved by the University of the Witwatersrand Committee for Research on Human Subjects. Written informed accent and consent were obtained from all subjects and their parents.
: Not applicable.
: The authors declare that they have no competing interests.
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