CDC Cutoff for Hepatitis B Immunity
The CDC defines protective immunity against hepatitis B as an anti-HBs (antibody to hepatitis B surface antigen) level of ≥10 mIU/mL. 1
Key Testing Parameters
- Testing method: Use a quantitative assay (such as ELISA) that can detect the protective concentration of ≥10 mIU/mL 1
- Timing: Perform testing 1-2 months after the final dose of the vaccine series 1
- Interpretation: Anti-HBs ≥10 mIU/mL indicates protective immunity and the person is considered immune 1
Important Clinical Considerations
Assay Variability
Different laboratory assays have different cutoff values, so the reported anti-HBs level may vary depending on which assay is used. 1 Always refer to the package insert of the specific test being used to determine the actual protective level. 1
Long-Term Protection in Immunocompetent Persons
Immunocompetent individuals who achieve anti-HBs ≥10 mIU/mL after completing the primary vaccine series have long-term protection and do not need further periodic testing or booster doses. 1, 2 This protection persists even if antibody levels subsequently decline below 10 mIU/mL, due to immunologic memory. 3, 4
Special Populations Requiring Different Management
Healthcare personnel (HCP): Should be tested for anti-HBs upon hire or matriculation if they have documentation of complete vaccination. 1 Those with anti-HBs <10 mIU/mL need additional vaccine doses. 1
Hemodialysis patients: Require annual anti-HBs testing, with booster doses administered when levels decline to <10 mIU/mL. 1, 5
Immunocompromised persons (HIV-infected, transplant recipients, chemotherapy patients): May need annual anti-HBs testing to assess concentrations. 1, 5
Infants born to HBsAg-positive mothers: Require specific revaccination protocols if anti-HBs is <10 mIU/mL after the primary series. 1
Common Pitfalls to Avoid
- Do not routinely retest or give booster doses to healthy immunocompetent individuals whose anti-HBs has declined below 10 mIU/mL after initially responding to vaccination 1, 2
- Do not confuse the protective threshold (≥10 mIU/mL) with assay-specific cutoff values that may differ between laboratories 1
- Do not delay vaccination while waiting for serologic test results in persons who need both testing and vaccination 1