Cross-sectional surveys
For each cross-sectional survey, we will use the surveillance area as a sampling frame to randomly select a sample of young people stratified by sex. Our initial sample size calculations were based on sampling At each survey, the study team will visit the sampled individuals at their homes to give them information about the study and invite them to participate. Those who are interested in participating will be asked to provide written informed consent if aged ≥ 18 years, or written assent and parental consent if aged < 18. Researchers will make up to four attempts at different times of the day to enrol the sampled individuals at home or a place of their choice. Based on our experience this will enable us to enrol 3200 (~ 80 per cluster) and reach our target sample size.After informed consent, participants will be asked to provide a blood sample for HIV testing (and viral load if positive), and to complete a 20–30-min interviewer-administered questionnaire. Sensitive questions will be self-completed. Questions will include awareness of HIV status; awareness and uptake of PrEP, voluntary medical male circumcision, ART and contraception; and exposure to youth groups, peer navigators, and SRH mobile clinics. We will also collect data on sociodemographics, sexual risk (e.g., number of partners, condom use, and transactional sex), reproductive health (e.g., contraception, pregnancy, fatherhood); and mental health (PHQ9, alcohol and drug use). Participants will also be asked for their consent to link their survey data with programmatic data collected from peer navigators, SRH mobile clinics, and PHCs in the surveillance area (Table Schedule of enrolment, interventions, and assessments for Thetha Nami ngithethe nawe stepped wedge cRCT