Antigenically variable viruses are responsible for some of the most contagious and economically important diseases that affect domestic livestock. The serious consequences of such diseases in terms of economic loss, and human and animal health, were clearly demonstrated by recent epizootics of foot and mouth disease, and outbreaks of avian influenza and bluetongue in the European Union (EU). For such diseases, government authorities need to be able to respond, if appropriate, by making use of vaccines that are suited to the epidemiological situation. The current EU regulatory framework is not well adapted for approval and maintenance of vaccines where the antigens included have to be chosen to reflect the epidemiological need. An extensive revision of the technical requirements for authorisation of veterinary medicinal products within the EU is currently underway. Additionally, a major revision of the regulations that control how such authorisations are kept up-to-date is about to start. This provides an ideal opportunity to introduce into EU legislation the concept of the 'multistrain dossier' whereby a potentially large number of approved strains may be included within a marketing authorisation and the final vaccines may be blended to include strains according to need. In addition, new strains may be added onto the marketing authorisation by means of a rapid regulatory procedure should new antigenic variants actually or potentially threaten the EU.