High prevalence of occult hepatitis B infection (OBI) among healthy children and their parents in Alborz province, Iran; Vertical OBI, myth or truth?

Background: Occult hepatitis B infection (OBI) has been described in various clinical settings including after hepatitis B virus (HBV) immunization. The purpose of study was to characterize the prevalence of OBI among immunized children from a subset of general population and the parents of OBI‐positive cases. Methods: Sera of 1200 children from general population who have been previously immunized by HBV vaccine were assayed for anti‐HBs. 660 were randomly selected for HBV DNA testing by different polymerase chain reaction (PCR) methods and were analysed by direct sequencing on surface genes. Results: None of participants were positive for HBsAg and anti‐HBc. 549 (45.7%) and 651 (54.3%) cases had anti‐HBs > 10 mIU/mL (responders) and < 10 mIU/mL (nonresponders) respectively. Of 660 selected specimens, 91 (16%) of children were positive for OBI. 23 (25.2%) and 68 (74.8%) of HBV DNA positive cases were belonged to responders and nonresponders, respectively, showing significant difference (P <.001). The mean levels of anti‐HBs in OBI‐positive and OBI‐negative groups, showed no considerable variations. The mean viral load for OBI‐positive cases showed substantial differences between responders and nonresponders (P =.007). Of 49 parents (98 individuals) of OBI‐positive children 11 (22%) and 18 (36%) were positive for anti‐HBc and anti‐HBs respectively. Molecular testing was positive in 32 subjects (16 couples, 32.6%). In total, 6 mothers and 11 fathers were positive for OBI. Conclusion: A proportion of OBI‐positive vaccinated children could be existed in different populations. This finding could be arisen from vertical HBV transmission or vertical OBI possibly from their parents. [ABSTRACT FROM AUTHOR]