Funding for this research was provided by:
Al Thasher Foundation (13431)
Received: 6 April 2020
Accepted: 1 September 2020
First Online: 2 October 2020
Ethics approval and consent to participate
: Ethical approval was obtained from the Ministry of Health and Social Welfare of Zanzibar, Tanzania (0001/2016) and from the Ethics Committee Northwest and Central Switzerland, Switzerland (ref: 2016–00839). Written informed consent was obtained from all the parents or guardians, and all adolescents provided verbal assent before enrolment.
: Not applicable.
: The authors declare that they have no competing interests.