Evaluation of the efficacy of an attenuated live vaccine based on virulent porcine reproductive and respiratory syndrome virus 2 in young pigs

The efficacy of the CA-2-MP120 vaccine, a cell culture-attenuated strain of virulent porcine reproductive and respiratory syndrome virus (PRRSV), was assessed in pigs.Despite the persistence of viremia in all vaccinated animals during the immunization period, the virus was not detected in vaccinated pigs following challenge.Furthermore, no pigs in the vaccinated group shed PRRSV nasally, orally or rectally throughout the experiment.Moreover, histopathological lung and lymph node lesions in the immunized group were much milder than those in the unimmunized and challenged group.These results indicated that CA-2-MP120 can provide effective protection against virulent wildtype PRRSV-2.