Disclosed herein are compositions and methods related to mutant viruses, and in particular, mutant influenza viruses. The mutant viruses disclosed herein include mutant M2 sequences, mutant BM2 sequences, and are useful in immunogenic compositions, e.g., as a quadrivalent vaccines. Also disclosed herein are methods, compositions and cells for propagating the viral mutants, and methods, devices and compositions related to vaccination.
