Vedolizumab in Pediatric inflammatory bowel diseases: a retrospective multi-center experience from the paediatric IBD Porto group of ESPGHAN - Ledder, O; De Meij, T; Martín De Carpi, J; Richmond, L; Cohen, S; Bronsky, J; Shaoul, R; Levine, A; Escher, J; Deridder, L; Assa, A; Ruemmele, F; et al. (12th Congress of the European Crohn's and Colitis Organisation (ECCO 2017), 2017)