TITLE OF THE INVENTION Method for quality control of an attenuated varicella live vaccine BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for quality control of an attenuated varicella live vaccine. More particularly, the present invention relates to a method for quality control of an attenuated varicella live vaccine, which comprises subjecting the genomic DNA of a sample varicella vaccine virus to sequence analysis and confirming that the genomic DNA of the sample varicella vaccine virus conserves the specific nucleotides without suffering mutation. By the use of the method of the present invention, it has become pos- sible to determine very accurately the qualification of an attenuated varicella virus as an active ingredient of an attenuated varicella live vaccine and, conse- quently, to conduct an exact quality control of the vaccines. Prior Art As is well known, attenuated varicella live vac- cines used today are produced from a seed strain of varicella virus which is derived from the attenuated varicella virus Oka strain (see Examined Japanese Pat- ent Application Publication No. 53-41202 and U.S. Pat- ent No. 3,985,615), and the attenuated live vaccines are used widely throughout the world (Requirements for Varicella Vaccine (Live) Adopted 1984; Revised 1993: WHO Technical Report Series, No. 848, pp. 22-38, 1994). To ensure the safety and effectiveness of the vaccine, the number of passages of a virus used for producing the vaccine is restricted under the control of a seed lot system, taking into consideration the potential ge- netic mutation which is likely to occur during the pas- sage. That is, the manufacturers are under an obliga- tion to produce varicella vaccines only from the virus derived from the approved seed virus for the live vari- cella vaccine, wherein the number of passages of the virus is not more than 10 as counted from the approved seed virus which is counted as 0 passage. In other words, the quality control and quality assurance of the attenuated varicella live vaccine rely upon the ful- fillment of the seed lot system by the manufacturers, and such a method for the quality control and quality assurance is not a method which can be traced and ana- lyzed by a person skilled in the art. Further, from the viewpoint of epidemiology which involves a tracing of the effects of the varicella vac- cine and a post-market surveillance (PMS), the vi- rological difference between the fresh wild-type strains isolated from the naturally infected varicella patients and the vaccine virus strains derived from the above-mentioned Oka strain needs to be determined, and various analyses, such as those utilizing immunological techniques and genetic engineering techniques, have been attempted for determination of the virological difference. For example, the following analyses have been reported: the difference in DNA sequence between the various VZV strains (Journal of Virology, 59, 660- 668, 1986; and