1. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, Athens, Greece
2. Department of Infection and Immunity, UCL, London, United Kingdom
3. Medical School, University of Cyprus, Nicosia, Cyprus
4. NIHR Biomedical Research Centre, UCLH/UCL, London, United Kingdom
5. Department of Clinical Virology, UCLH, London, United States
6. Division of Infection and Immunity, Faculty of Medical Sciences, UCL and Farr Institute of Health Informatics Research, London, United Kingdom
7. Transmission Reduction Intervention Project, Athens site, Athens, Greece
8. National Development and Research Institutes, New York, United States