A cell contacted with a plurality of orthomyxovirus vectors comprising: (i) a vector comprising a promoter operably linked to an influenza virus PA cDNA linked to a transcription termination sequence, (ii) a vector comprising a promoter operably linked to an influenza virus PB 1 cDNA linked to a transcription termination sequence, (iii) a vector comprising a promoter operably linked to an influenza virus PB2 cDNA linked to a transcription termination sequence, (iv) a vector comprising a promoter operably linked to an influenza virus HA cDNA linked to a transcription termination sequence, (v) a vector comprising a promoter operably linked to an influenza virus NP cDNA linked to a transcription termination sequence, (vi) a vector comprising a promoter operably linked to an influenza virus NA cDNA linked to a transcription termination sequence, (vii) a vector comprising a promoter operably linked to an influenza virus M cDNA linked to a transcription termination sequence, (viii) a vector comprising a promoter operably linked to an influenza virus NS cDNA linked to a transcription termination sequence, (ix) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PA polypeptide and linked to a transcription termination sequence, (x) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PB1 polypeptide and linked to a transcription termination sequence, (xi) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PB2 polypeptide and linked to a transcription termination sequence, and (xii) a vector comprising a promoter operably linked to a DNA segment encoding an influenza NP polypeptide and linked to a transcription termination sequence wherein said cell expresses said orthomyxovirus. (i) a vector comprising a promoter operably linked to an influenza virus PA cDNA linked to a transcription termination sequence, (ii) a vector comprising a promoter operably linked to an influenza virus PB 1 cDNA linked to a transcription termination sequence, (iii) a vector comprising a promoter operably linked to an influenza virus PB2 cDNA linked to a transcription termination sequence, (iv) a vector comprising a promoter operably linked to an influenza virus HA cDNA linked to a transcription termination sequence, (v) a vector comprising a promoter operably linked to an influenza virus NP cDNA linked to a transcription termination sequence, (vi) a vector comprising a promoter operably linked to an influenza virus NA cDNA linked to a transcription termination sequence, (vii) a vector comprising a promoter operably linked to an influenza virus M cDNA linked to a transcription termination sequence, (viii) a vector comprising a promoter operably linked to an influenza virus NS cDNA linked to a transcription termination sequence, (ix) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PA polypeptide and linked to a transcription termination sequence, (x) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PB1 polypeptide and linked to a transcription termination sequence, (xi) a vector comprising a promoter operably linked to a DNA segment encoding an influenza PB2 polypeptide and linked to a transcription termination sequence, and (xii) a vector comprising a promoter operably linked to a DNA segment encoding an influenza NP polypeptide and linked to a transcription termination sequence wherein said cell expresses said orthomyxovirus.