Why we need more collaboration in Europe to enhance post-marketing surveillance of vaccines av 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