The present invention relates to isolated influenza virus strains suitable for increased vaccine production for mammals. The influenza virus strains contain at least one modified influenza protein that results in increased production of the influenza virus from a mammalian host cell, such as a vero cell. The present invention also relates to the vaccines produced from the influenza virus strains. The present invention further relates to isolated modified influenza proteins and isolated nucleic acid molecules that encode for the modified influenza proteins.
