Hepatitis B core total antibody (HBcAb) detects antibodies against the hepatitis B core antigen, which is part of the hepatitis B virus (HBV) itself rather than the surface coat. Core antibodies develop during active HBV infection and persist for life after infection resolves, serving as a lasting marker of past exposure to hepatitis B.
Unlike hepatitis B surface antibodies (HBsAb) produced by vaccination, core antibodies are only produced in response to actual infection with HBV — not vaccination. This makes HBcAb a specific marker of prior natural infection. Detecting HBcAb alongside other hepatitis B markers (HBsAg, HBsAb, HBeAg, HBV DNA) is essential for fully characterising a person's hepatitis B status.
FAQs
Does vaccination produce a positive HBcAb result?
No. Hepatitis B vaccination only produces HBsAb (surface antibodies). HBcAb is only produced in response to natural infection with the hepatitis B virus. If you are vaccinated and have negative HBcAb with positive HBsAb, this confirms vaccine-induced immunity without prior infection.
What does isolated HBcAb mean?
Isolated HBcAb (positive HBcAb, negative HBsAg, negative HBsAb) is found in people with very remote past resolved HBV infection where surface antibodies have waned, in people in the window period of acute infection, and rarely in occult chronic HBV infection. HBV DNA testing can clarify whether active virus is present.
Can HBV reactivate if I have positive HBcAb?
Yes. In people with isolated HBcAb who undergo immunosuppressive therapy (chemotherapy, biologics, organ transplant), dormant HBV can reactivate and cause severe hepatitis. Antiviral prophylaxis is typically given in this situation.
What is the window period in hepatitis B?
The window period is the time after HBsAg has cleared but before HBsAb has appeared. During this phase, HBcAb may be the only positive marker. Most people progress from the window period to either resolved infection (HBsAb positive) or chronic infection (HBsAg re-appears) within weeks to months.
