The invention relates to the field of influenza virus and the vaccination against flu. The invention provides a conditionally defective influenza virus particle having seven different influenza nucleic acid segments. The invention also provides a conditionally defective influenza virus particle lacking an influenza nucleic acid segment selected from the group of segments essentially encoding acidic polymerase (PA), the basic polymerase 1 (PB1 ) and the basic polymerase 2 (PB2). In particular, the invention provides defective influenza virus particles having seven different influenza nucleic acid segments and lacking an influenza nucleic acid segment essentially encoding acidic polymerase. Furthermore, the invention provides use of a composition comprising a defective influenza virus particle according to the invention for the production of a pharmaceutical composition directed at generating immunological protection against infection of a subject with an influenza virus, and provides a method for generating immunological protection against infection of a subject with an influenza virus comprising providing a subject in need thereof with a composition comprising such defective influenza virus particle.
