[Effects of virus mutations caused by passages on vaccinal immunogenicity].

The live attenuated viral vaccines are developed by adapting viruses in the different culture conditions or in the different hosts through several passages. Success of adaptations is based on the viral nature that viruses mutate easily. Once the vaccine strain is established, it should be maintained stably. Since the property that viral genome mutates easily is a survival strategy of viruses, it is inevitable for viruses to generate mutants at random in replication step. It is possible that mutations occurred in the vaccine strain during the passages influence on attenuation property or on immunogenicity of the vaccine. Therefore, vaccines should be produced according to the fixed operation protocol within the limited passages. In addition, some vaccines are requested to be measured the percentage of mutants in the bulk material. If the mutants more than approved are detected, the bulk material is controlled not to be used for the vaccine.