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.