Occult Hepatitis B Virus Infection In Hepatitis B Vaccinated Children In Southwest China

Objective: The aim of this study was to examine the prevalence of Occult HBV infection(OBI) in hepatitis B virus(HBV) vaccinated HBV surface antigen(HBsAg).-negative children with HBsAg-positive father and/or mother in southwest China, analyze sequences and relevant factors for OBI, which was the foundation and basis for the epidemiological study of OBI in hepatitis B vaccinated children Methods: Samples of HBsAg-negative sera(n=211) obtained from HBV-vaccinated children with HBsAg-positive father and/or mother were collected. Serological tests for HBV markers were performed using commercial CMIA kits. Children younger than 8 months or with no confirmed record of vaccination were excluded. The Surface, Pre-S, Core/pre-core, and X genes of HBV were amplified by nested PCR and analyzed by direct sequencing. Samples which were positive for at least two of the four(Surface, Pre-S, X, and Core/pre-core) HBV regions were considered to have OBI. HBV DNA was quantified by Real-time PCR further. Clinical data such as feeding practices and manner of birth were collected to analyze the prevalence and relevant factors. Results: A group of 186 vaccinated children was included and analyzed. The prevalence of OBI in HBV vaccinated HBsAg-negative children with HBsAg-positive father and/or mother in southwest China was 4.3%. Of eight OBI cases, six(75%) had a HBV infected father while two(25%) had a HBV infected mother. According to phylogenetic analysis and genotyping tool of NCBI, two sequences were genotype C and one of them was serotype adrq, three sequences were genotype B and other three were genotype B/C. Totally, six sequences were serotype adw2. Two children harbored ‘a’ determinant variants and one of them with a high level of HBV DNA was categorized as “false” OBI. Several mutations were harbored in MHR. HBIG did not help to reduce the prevalence of OBI. Breast feeding and vaginal delivery were not risk factors for OBI, while Breast feeding could help to the production of HBs Ab. And the OBI children were in normal levels of ALT and AST. Conclusion: The present study shows that occult hepatitis B virus infection is found in hepatitis B vaccinated HBsAg-negative children from HBs Ag-positive parents. Mutations in HBV S region could be the cause of OBI. Several OBI children with HBV carrier fathers were found in this study. Breast feeding and vaginal delivery had no effect on the prevalence of OBI. The immunization program in China is effective. And it still be important to pay more attention to the screen of HBV as well as OBI in hepatitis B vaccinated children, particularly those that are HBsAg-negative with HBV carrier parents.