分析受乙肝疫苗保护后部分儿童的“免疫无效”现象。方法：采用巢式ＰＣＲ－ＳＳＣＰ银染技术对１５例曾受疫苗保护的儿童血清中ＨＢＶＤＮＡＳ基因片段进行研究。结果：在ＨＢｓＡｇ阴性血清中存在ＨＢＶＳ基因点突变，该突变位于从ＨＢＶ基因组ＥｃｏＲＩ位点算起的第３６７—７６９核苷酸区域内。结论：在肝癌高发地区启东发现存在 ＨＢＶ逃脱变异。疫苗刺激机体所产生的抗体不能中和入侵的 ＨＢＶ ａ决定簇并阻断 ＨＢＶ感染，可由病毒逃脱变异所致。该变异产生的原因及其预防对策尚在研究之中。 Analysis of the “immune ineffectiveness” of some children protected by hepatitis B vaccine. Methods: Nested PCR-SSCP silver staining technique was used to study the serum HBVDNAS gene fragments in 15 children who had been vaccinated. Results: There was a point mutation in the HBVS gene in HBsAg-negative sera within the region of nucleotides 367-769 from the EcoRI site of the HBV genome. Conclusion: HBV escape mutation was found in Qidong, a high incidence area of ​​liver cancer. Antibodies produced by vaccines that stimulate the body do not neutralize the invading HBV a determinant and block HBV infection, as a result of the virus escaping the mutation. The causes of the mutation and its preventive measures are still under study.