This is incorporated into an emulsion with mineral oil orvegetable oil, and is administered intramuscularly or subcutaneously. Individual birds thus receive a
standard dose. There is no subsequent spread of virus or adverse respiratory reactions. Both virulent and
avirulent strains are used as seed virus although, from the aspect of safety control, the use of the latter
appears more suitable. As no virus multiplication takes place after administration, a much larger amount of
antigen is required for immunisation than for live virus vaccination.