the invention relates to the field of influenza vaccine production . influenza vaccines have been produced in embryonated hens &# 39 ; eggs for over 50 years , but recently there have been considerable efforts to develop cell culture systems for vaccine production . in one embodiment , the invention provides a nucleic acid comprising an influenza gene segment and a bacteriophage polymerase promoter or a complementary strand of said nucleic acid , and a cell comprising such a nucleic acid capable of producing desired influenza virus . in another embodiment , the invention provides a composition comprising a cell or material derived from a cell according to the invention and a virus or material derived from a viral particle according to the invention .