Active immunisation of sheep and cattle to prevent viraemia* and to reduce clinical signs caused by bluetongue virus serotype 8.*(below the level of detection by the validated RT-PCR method at 3.14log10 RNA copies/ml, indicating no infectious virus transmission). Onset of immunity has been demonstrated 3 weeks after the primary vaccination course. The duration of immunity for cattle and sheep is 1 year after the primary vaccination course. The duration of immunity is not yet fully established in cattle or sheep, although interim results of ongoing studies demonstrate that the duration is at least 6 months after the primary vaccination course in sheep.