| http://www.w3.org/ns/prov#value | - One of the vaccines useful in this method is a vaccine which comprises a suitable carrier and an effective immunizing amount of a recombinant IBR virus comprising viral DNA from a naturally-occurring IBR virus in which DNA encoding gpG glycoprotein has been altered or deleted and DNA encoding the gpE glycoprotein has been altered or deleted so that upon replication the recombinant IBR virus produc
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