Though attenuated virus vaccines work well, no vaccine offers 100 % protection against disease. Their greatest problem is that the attenuated virus is indistinguishable from infections from the wild. The inability to effectively screen the herd in which a sick pig is discovered results in wholesale culling.
減毒疫苗的免疫效果雖佳，但任何疫苗都不可能百分之百預防，而其最大缺點則是無法與野外感染的抗體區分，一旦豬場出現病豬，在無法及早篩檢區隔的情況下，只好進行整場撲殺。