The primary objective of this project was to test a PRRS vaccine based on a PRRSV anti-idiotypic antibody. Subsequent to the primary objective, the intent was to determine whether effective vaccines could be produced using this technology and develop a diagnostic test to differentiate between vaccinated and field virus-infected pigs. However, a test of the vaccine found no difference in the level / duration of viremia or in the humoral immune response between vaccinates and non-vaccinates. Therefore, objectives 2 and 3 were not pursued and the residual resources were returned to the National Pork Board.