The present invention relates generally to infectious pancreatic necrosis virus (IPNV) and specifically to further characterisation of the genetic stability of IPNV genome. More in particular, the invention relates to greater appreciation and understanding of the frequency of mutagenesis and codon interactions that influence the replication capabilities, virulence and immunogenicity of the virus. There is provided for the first time a method for developing a commercially applicable IPNV vaccine and a vaccine comprising the IPNV genome carrying particular mutations and codons. There are also described uses in prophylaxis or treatment of infectious pancreatic necrosis (IPN) disease.
