Attenuated influenza virus vaccine strain and vaccine for distinguishing infection and immunity

The invention provides an attenuated influenza virus vaccine strain and vaccine for distinguishing infection and immunity, and belongs to the technical field of biological products. The influenza virus attenuated strain is obtained by mutating an M gene on the basis of an influenza virus strain containing an A/B chimeric NA gene; the mutation comprises the deletion of a DNA fragment with the length of more than 8bp behind the 3'end of the CCTTCC sequence. The influenza virus attenuated strain can grow in MDCK-M2 cells, but cannot grow in MDCK cells lacking M2, has a good attenuation effect, and overcomes biological safety risks caused by the fact that non-replication defective viruses need to be cultured for producing highly pathogenic avian influenza inactivated vaccines; after SPF chicken is immunized by the prepared inactivated vaccine, a relatively high level of HAI titer is detected in serum of the immunized chicken, which shows that the strain generated by the attenuated influenza virus strain is safe a