General purpose and objectives Classical swine fever (CSF) is a highly contagious disease that causes huge economical losses and animal welfare concerns worldwide. Generally, vaccination is an effective and safe method to control the disease. Following vaccination the pig’s immune system develops antibodies that are significant part of the protection. However, vaccination with the only live attenuated vaccines existing on the market that contain a whole CSF virus (CSFV) with reduced infectivity, leads to production of an antibody response that does not differ from the antibody response developed after infection. Thus, implementation of these vaccines in case of outbreak will not give the possibility to differentiate infection in vaccinated animals (DIVA). For countries like Denmark, which are heavily dependent upon export of pigs and pig products the use of these traditional vaccines, will hamper the ability to proof a disease free status by serosurveillance, as all vaccinated piglets will be seropositive. This PhD-project is a part of an EU project (CSFV_goDIVA grant no 227003) that has been funded by the European Commission with a main goal to develop and test to a level of registration a new DIVA vaccine candidate. The vaccine candidate “CP7E2alf” is intended for either intramuscular vaccination of domestic pig or for bait vaccination of wild boar. In this thesis as part of the clinical testing of the injection vaccine the efficacy of “CP7E2alf” was evaluated in young piglets that were positive for maternally derived antibodies (MDA). These antibodies were obtained with colostrum from their mothers vaccinated with traditional live attenuated vaccine C-strain (Riems). The promising results concerning the safety and the efficacy of the candidate DIVA vaccine showed new opportunities for control of a possible CSF outbreak that will have reduced impact on the export.