1. Postgraduate Program in Epidemiology, Federal University of Pelotas, Pelotas, Brazil
2. Nossa Senhora da Conceição Children’s Hospital, Brazilian Ministry of Health, Porto Alegre, Brazil
3. Departmento de Medicina Preventiva, Universidade de São Paulo, São Paulo, Brazil
4. Department of Paediatrics, The Hospital for Sick Children, Research Institute, University of Toronto, Toronto, Ontario, Canada