The present invention relates, in general, to materials and methods for production of an improved vaccine against influenza virus, wherein the vaccine comprises a reassortant virus having a hemagglutinin gene and a neuraminidase gene from the same influenza A virus subtype or influenza B strain of virus and internal genes from a different influenza A virus subtype or influenza B strain of virus. In one aspect, the HA and NA genes and the internal genes are from a highly pathogenic H5N1 strain of influenza A.