Ethical considerations
The study protocol was approved by the Biomedical Research Ethics Committee of the University of KwaZulu-Natal (BREC/00000473/2019), the University College of London Research Ethics Committee (5672/003), and the Mass General Brigham Institutional Review Board (2021P002574). Written informed consent was obtained from all participants 18 years or older; verbal assent with written informed consent from a parent or guardian was obtained for all participants aged 16 to 17 years.