The invention relates to the field of influenza vaccine production. Influenza vaccines have been produced in embryonated hens' eggs for over 50 years, but recently there have been considerable efforts to develop cell culture systems for vaccine production. The invention provides a nucleic acid comprising an influenza gene segment and a bacteriophage polymerase promotor or a complementary strand of said nucleic acid, and a cell comprising such a nucleic acid capable of producing desired influenza virus. Furthermore, 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.