Received: 4 July 2019
Accepted: 19 January 2020
First Online: 29 January 2020
Ethics approval and consent to participate
: Ethical approvals to conduct the study was obtained from both the National Institute for Medical Research (NIMR) on July 4th, 2012 and Muhimbili University of Health and Allied Sciences (MUHAS) on March 16, 2012, and renewed each year till 2015. All participants signed informed consent before they were enrolled in the study.
: Not apply.
: The author declared no potential competing of interest with respect to the research, authorship, and/or publication of this article.