1. School of Social and Community Medicine, University of Bristol,
2. Bristol Sexual Health Centre, University Hospitals Bristol NHS Trust, and
3. National Institute for Health Research Health, Protection Research Unit in Evaluation of Interventions in partnership with Public Health England, University of Bristol, United Kingdom; and
4. Department of Epidemiology, Tulane University School of Public Health and
5. Department of Medicine, Louisiana State University Health Sciences Center, New Orleans