Successful immunization programmes have reduced the burden of a number of infectious diseases on a global scale. Yet, as the fear of sequelae of vaccine-preventable diseases diminishes in the public, the focus of interest has shifted towards true and alleged "side effects". Maintaining confidence in the necessity, tolerability and safety of immunizations is of paramount importance today. This requires, amongst other prerequisites, precise definitions of "adverse events following immunization". In Europe, a collaborative effort named EUSAFEVAC in concert with the globally active "Brighton Collaboration" has been initiated. Volunteers from academic institutions, vaccine licensing authorities, public health institutes, governmental organizations, safety units within the vaccine manufacturing industry as well as practising physicians are working together to achieve this goal.[résumé auteur]