Methods for enhancing the production of viral vaccines in animal cell culture are described. These methods rely on the manipulation of the cellular levels of certain interferon induced antiviral activities, in particular, cellular levels of double-stranded RNA (dsRNA) dependent kinase (PKR) and 2'-5' oligoadenylate synthetase (2-5A synthetase). In cell cultures deficient for PKR or 2-5A synthetase, viral yield is enhanced by several orders of magnitude over cell cultures with normal levels of these proteins making these cell cultures useful for the production of viral vaccines.