The role of vaccines for PRRS control and PRRSV eradication

After its first appearance in the late eighties, porcine reproductive and respiratory syndrome virus (PRRSV) caused for several years huge financial losses worldwide. Vaccines were developed shortly after, with big success. However, due to genetic drift, PRRSV was escaping more and more from vaccination immunity. At present, the original vaccines are no longer giving a full control of PRRS. Therefore, there is a need for adaptable vaccines that can be regularly updated. One should even think in the direction of auto-vaccines, based on farm-specific PRRSV isolates. Desperation drove farmers and veterinarians in the direction of ‘controlled infections’ with farm isolates with biosafety problems. Recently, a new methodology has been developed in our laboratory for adaptable inactivated vaccines with success. These vaccines allow to booster existing immunities in sows, giving a strong protection in sows and in the offspring via colostral immunity. This vaccine will not be the wonder product for naive animals. In this context, adaptable live vaccines are necessary. Because PRRSV starts with a replication in the respiratory tract, the induction of a local immunity would be most suitable. At present, adaptable attenuated and vector vaccines are under development in the author’s laboratory, based on new cellular and molecular insights of the PRRSV pathogenesis and immunity. A combination of adaptable attenuated/vector and inactivated vaccines will be the best tools to control and, if efficient enough, to eradicate PRRS.