Background: No or low hepatitis B (HB) vaccine response is more frequent in infants from HBsAg(+) mothers than those from HBsAg(-). Our previous study found temporary positivity of HBsAg in infants from HBsAg(+) mothers. In this study, we hypothesized that HBsAg in infant blunt immune response to standard hepatitis B vaccination.
Methods: A total of 328 consecutive HBsAg(+) mothers and their offspring were enrolled. Blood samples were taken from mothers and their infants and quantified for HBsAg, anti-HBs titer and HBV DNA load concentration; Placenta samples were collected to stain for HBsAg.
Results: First, 6.7% infants (22/328) showed anti-HBs titer lower than 10 mIU/mL after HB vaccination (non-response to HB vaccine). HBsAg(+) newborns showed higher risk of non-response than HBsAg(-) infants (13.0% versus 5.0%, p = 0.016). Infants from high HBsAg titer mothers displayed higher risk of HBsAg positivity at birth than those from low titer mothers (45.3% versus 2.8%, p < 0.001). HBsAg titer in mothers of HBsAg(+) newborns was much higher than mothers of HBsAg(-) newborns (p < 0.001). All those data supported HBsAg can be transferred through placenta. Our hypothesis was further reinforced by immunostaining with specific antibody against HBsAg, a substantial higher prevalence (87.5% versus 30.8%, p = 0.024) and stronger immunostaining (p = 0.008) was demonstrated in HBsAg(+) group comparing with placenta of the HBsAg(-) group.
Conclusion: No response to HB vaccine in infants of HBsAg(+) mothers was associated to the transplacental transfer of HBsAg.
Keywords: HBsAg; hepatitis B vaccine; immune response; placenta.