Objective To evaluate the effect of production site change of vaccine production on the quality of live attenuated varicella vaccine at the molecular level.Methods Using next-generation sequencing(NGS),the varicella-zoster virus(VZV)Oka strain virus seed(VW-before,SYVW-after)and vaccine bulk(P-before,YZP-after)produced before and after prodution site change were subjected to DNA extraction,purification,library construction and sequencing,and the quality control of the sequencing results were performed.Taking gene sequence of Dumas strain registered in GenBank(NC＿001348)as the position reference genome,the whole gene sequences of the four samples before and after prodution site change were compared with the Oka strain virus to obtain the mutation sites,base changes and variant allele frequency(VAF),and the consistency of the samples was evaluated.Results All the sequencing depth of the four samples was more than1 500 ×,and the GC content of the virus seed and vaccine bulk was about 46%,indicating that the sequencing quality was high.The mutation sites and base composition of the gene sequences of virus seed and vaccine bulk were consistent before and after prodution site change,and the VAF was close.Pairwise comparison of correlation coefficients was highly correlated,and the correlation coefficients were significantly different(each R~2≥ 0.990,each P < 0.001).Conclusion NGS test showed that the changes in vaccine production process have no effect on the quality of live attenuated varicella vaccine.