1. Department of Pediatrics, Faculty of Medicine, Universidad de Chile, Santiago, Chile
2. Infectious Diseases Unit, Hospital de niños Dr. Exequiel González Cortés, Santiago, Chile
3. Centre for Epidemiology and Microbiology, National Institute of Public Health, Prague, Czech Republic
4. Vaccine Medical Development and Scientific/Clinical Affairs, Pfizer Inc, Paris, France
5. Vaccine Medical Development and Scientific/Clinical Affairs, Pfizer Inc, Collegeville, PA, USA
6. Vaccine Medical Development and Scientific/Clinical Affairs, Pfizer Ltd, Tadworth, UK