Although modified live - attenuated vaccines ( MLVs ) and inactivated vaccines against PRRSV have been available for more than a decade ,
The efficacies of these vaccines especially against heterologous strains remain questionable :
Although modified live - attenuated vaccines ( MLVs ) and inactivated vaccines against PRRSV have been available for more than a decade , the disease remains difficult to control .
The efficacies of these vaccines especially against heterologous strains remain questionable :