The present invention provides a method for producing immunogenic synthetic oligopeptides that are formed by minimal immune determinants uniquely present in antigens of interest and are useful for evoking specific, effective and non-crossreactive immune responses in immunotherapies and immunodiagnostics. The determinants are connected to each other by linkers and wherein that each linker contains at least one element that is not a human aminoacid. The invention also provides a pharmaceutical preparation, such as a vaccine, which comprises said immunogenic synthetic oligopeptides. It also covers veterinary and agricultural preparations.