Porcine Reproductive and Respiratory Syndrome (PRRS) imposes a huge financial burden on the swine industry. Thus, there is a clear and immediate need for improved PRRS virus (PRRSV) vaccines. Our group has proposed a new classification scheme for PRRSV strains that allows for immunological differentiation based on level of GP5 glycosylation. This classification based on glycantype has allowed us to choose PRRSV strains that offer the best chance of protection against PRRS.