Hepatitis B surface antibody (anti-HBs)
Also called: Hepatitis B surface antibody, Anti-HBs, HBsAb, HBs antibody
The protective antibody against hepatitis B. It appears after successful vaccination or recovery from past infection, so it is the test used to check whether you are immune to hepatitis B. Unlike most tests, a high level is the good result — it means you are protected.
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What does Hepatitis B surface antibody (anti-HBs) measure?
Hepatitis B surface antibody (anti-HBs) is the antibody the immune system makes against the outer 'surface' protein of the hepatitis B virus. Its presence means the immune system can neutralise the virus, so it is the marker of immunity. Anti-HBs appears in two situations: after successful vaccination against hepatitis B (the vaccine contains this surface protein, and the body responds by making the antibody), and after recovering from a past hepatitis B infection (alongside another antibody, anti-HBc). It is therefore used to answer a practical question — 'am I immune to hepatitis B?' — for example when checking a healthcare worker's vaccine response, screening before starting certain treatments, or confirming protection in someone at risk. A level at or above the accepted threshold (usually 10 mIU/mL) indicates protection. It is interpreted alongside the other hepatitis B markers: the surface antigen (which signals active infection) and the core antibody (which marks past exposure), so that immunity from vaccination can be told apart from immunity after infection.
What does a high Hepatitis B surface antibody (anti-HBs) level mean?
- Immunity to hepatitis B — the protective, reassuring result; from vaccination or past resolved infection.
- A successful vaccine response — the common reason it is checked.
- Recovery from past hepatitis B — anti-HBs positive together with core antibody (anti-HBc).
What does a low Hepatitis B surface antibody (anti-HBs) level mean?
- Not immune — no protection has developed; may need (re)vaccination.
- A non-responder or waned response to the vaccine — some people need an extra course.
- Never vaccinated or exposed — the expected result before immunisation.
When to discuss with a doctor
Anti-HBs is checked to confirm immunity to hepatitis B — after vaccination (especially in healthcare workers, people on dialysis, or others at risk), or as part of assessing hepatitis B status. A level at or above the threshold is reassuring: it means you are protected. A level below the threshold means you are not currently immune, and vaccination or a booster is usually recommended, guided by your doctor and read together with the other hepatitis B markers. Because this is one of the few tests where a high value is the desirable one, a 'positive' result here is good news. Mediora.AI shows anti-HBs alongside the hepatitis B surface antigen and core antibody so your immunity status is read as a set; decisions about vaccination belong with your doctor.
Related markers
Commonly confused with
- Hepatitis B surface antigen (HBsAg) The antigen is a piece of the virus itself: finding it means the infection is present. The antibody is your immune response: finding it usually means you are protected, after vaccination or a past infection.
- Hepatitis B core antibody (anti-HBc) Both are antibodies, but they tell different stories: the core antibody appears only after a real infection, the surface antibody also after vaccination. Core positive with surface positive means you met the virus and recovered; surface alone usually means vaccination.