1. Department of Health Sciences, University of Florence, Florence, Italy
2. Department of Public and Global Health, Division of Infectious Diseases, World Health Organization Collaborating Centre for Traveller’s Health, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland
3. Division of Epidemiology, Human Genetics and Environmental Sciences, University of Texas School of Public Health, Houston, TX, USA
4. Medical Faculty, Ludwig-Maximilians-University, Munich, Germany
5. GSK, Wavre, Belgium
6. GSK, London, UK
7. Department of Social Science, Health and Medicine, King’s College London, London, UK
8. Centre for the Evaluation of Vaccination, VAXINFECTIO, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium