Patient's question:
Born just 10 days ago, it was discovered during a postnatal health check that the mother had hepatitis B (HBV) surface antigen (HBsAg) positivity. During the pregnancy, no preventive measures were taken. On the third day after birth, the baby was tested for the five hepatitis B markers (HBsAg, HBsAb, HBeAg, HBeAb, and HBcAb), with only the fifth marker (HBcAb) being positive. The other markers were negative: HBsAg (negative), HBsAb (negative), HBeAg (negative), HBeAb (negative), and HBcAb (positive). The hepatitis B immune globulin (HBIG) was administered on the third day after birth.Dear doctor,
1. Has the baby already contracted hepatitis B?
2. Why does the baby need to receive the third dose of HBIG at 15 days of age?
3. Is it still effective to vaccinate the baby with the hepatitis B vaccine?
I urgently look forward to your help. Thank you!
Doctor's answer:
The baby cannot be diagnosed with hepatitis B. A positive HBCAb (hepatitis B core antibody) suggests acute HBV infection during the core window period. The core antibody (HBCAb) can serve as a marker for HBV infection. The detection of HBCAb in the serum indicates that the virus is currently active or has previously replicated. It is the first antibody to reappear among the "four and a half pairs," typically appearing 2-4 weeks after the reappearance of HBsAg. When HBsAg disappears but HBsAb has not yet reappeared, HBCAb is often the only antibody detected. Therefore, this stage is clinically referred to as the window period.