Hepatitis B Surface Antibody
Anti-HBs· also: HBsAb, HBV surface antibody
Clinical Overview
Anti-HBs (Hepatitis B Surface Antibody) indicates immunity to Hepatitis B — either from successful vaccination or from natural recovery after infection. It is the only antibody produced after vaccination and is the marker used to assess vaccine-induced immunity. A level of ≥10 IU/L is considered protective immunity against Hepatitis B.
Why This Test Matters
Anti-HBs is measured to confirm adequate immune response after HBV vaccination, especially in high-risk groups (healthcare workers, dialysis patients, immunocompromised individuals). Response rates to the standard 3-dose HBV vaccine series are >90% in healthy adults under 40, declining with age and immunosuppression. Non-responders to the standard series (Anti-HBs <10 IU/L) should receive an additional 3-dose series; if still non-responding, they remain susceptible to HBV and should be counseled about ongoing risk. In dialysis patients and immunocompromised patients, higher anti-HBs thresholds (>100 IU/L) may be required for reliable protection.
Reference RangesWHO/IFCC standards
| Reference Range | Unit | Notes |
|---|---|---|
| 10 – 999 | IU/L | Protective ≥10 IU/L |
Also reported in: mIU/mL.
What Causes Abnormal Results?
High Anti-HBs Causes
- Successful Hepatitis B vaccination (most common)
- Natural recovery from acute Hepatitis B infection (Anti-HBs develops alongside Anti-HBc)
Low Anti-HBs Causes
- Non-response to HBV vaccine (<10 IU/L) — occurs in ~5–10% of healthy adults
- Waning immunity years after vaccination (levels decline over time)
- Immunosuppression reducing vaccine response (HIV, renal failure, chemotherapy)
- Genetic non-responders (rare HLA-related inability to mount anti-HBs response)
Signs & Symptoms to Watch For
How to Prepare for This Test
No fasting required. For best assessment of vaccine response, measure Anti-HBs 4–8 weeks after completing the vaccine series. Anti-HBs naturally declines over years — periodic booster doses may be recommended for high-risk individuals.
Factors That Can Affect Results
- Anti-HBs measured within days of an HBV vaccination dose may reflect passive transfer rather than immune response
- Recent HBIG (Hepatitis B Immunoglobulin) administration transiently raises Anti-HBs without true immunization
Related Topics
Frequently Asked Questions
My Anti-HBs result came back as 8 IU/L — am I protected?
No. A level below 10 IU/L is considered non-protective (non-response to vaccination). You should receive an additional series of 3 HBV vaccine doses (revaccination series). After completing the second series, recheck Anti-HBs. Approximately 50–70% of initial non-responders will develop protective immunity after revaccination. If you remain <10 IU/L after two complete series, you are classified as a non-responder and should be counseled about susceptibility and appropriate precautions (especially if a healthcare worker).
How long does Hepatitis B vaccine protection last?
Immunity from a complete 3-dose HBV vaccine series is very long-lasting — immune memory persists for decades even as Anti-HBs levels decline below 10 IU/L. Booster doses are not routinely recommended for immunocompetent individuals. However, healthcare workers, dialysis patients, and HIV-positive individuals should have their Anti-HBs checked periodically because their immune responses are less durable. If Anti-HBs drops below 10 IU/L in these high-risk groups, a booster dose is recommended.