Why we need more collaboration in Europe to enhance post-marketing surveillance of vaccines by Sturkenboom, M, Bahri, P, Chiucchiuini, A, Grove Krause, T, Hahné, S, Khromava, A, Kokki, M, Kramarz, P, Kurz, X, Larson, H, De Lusignan, S, Mahy, P, Torcel-Pagnon, L, Titievsky, L, Bauchau, V