Occult hepatitis B virus infection in children born to HBsAg-positive mothers after neonatal passive-active immunoprophylaxis

Background: Occult hepatitis B virus infection (OBI) is a well-recognized clinical entity characterized by the detection of HBV DNA in serum and/or liver in the absence of detectable HBsAg. Diagnosis of OBI requires a sensitive HBV DNA assay. Aim: We aimed at determining the frequency of OBI in infants, born to HBsAg-positive mothers, who received immunoprophylaxis at birth. Methods: Sixty-four infants and children, born to HBsAg-positive mothers, who received hepatitis B immunoglobulin and HBV vaccine within 48 h after birth, were tested for HBV serological profile and HBV DNA by real-time PCR at least 1 month after last dose of HBV vaccine and not before 6 months of age. Results: The median age of the studied infants and children was 8 months, ranging from 6 to 132 months; 54.7 % were females. HBV DNA was detected in 2 infants. One case had OBI; she was negative for HBsAg, anti-HBc total, HBeAg and was positive for anti-HBs (titer 267 mIU/mL) with low level of viremia (HBV DNA 1.13 x 103 IU/mL). Another infant showed immunoprophylaxis failure with positive HBsAg, anti-HBc total, HBeAg, negative anti-HBe and anti-HBs; HBV viral load was 1.7 × 108 IU/mL. Both mothers were HBsAg and HBeAg-positive. Conclusion: OBI may occur in infants born to HBsAg-positive mothers despite the receipt of immunoprophylaxis. OBI was detected in a low frequency in the present study. Anti-HBs positivity does not exclude OBI.