How is hepatitis B (HB) immunization status tested?

Testing for Hepatitis B Immunization Status

Measure antibody to hepatitis B surface antigen (anti-HBs) using a quantitative assay 1-2 months after the final vaccine dose, with levels ≥10 mIU/mL indicating protective immunity. 1

Who Should Be Tested

Not everyone requires postvaccination testing. According to the CDC, testing is specifically recommended for: 1

• Healthcare personnel and public safety workers at risk for blood or body fluid exposure 1
• Hemodialysis patients and those who might require outpatient hemodialysis 1
• Immunocompromised persons including HIV-infected individuals, hematopoietic stem-cell transplant recipients, and those receiving chemotherapy 1
• Sex partners of HBsAg-positive persons 1
• Infants born to HBsAg-positive mothers 1

Testing Method and Timing

The test must be performed 1-2 months after administration of the final vaccine dose using a quantitative method that detects protective concentrations (≥10 mIU/mL), such as enzyme-linked immunosorbent assay (ELISA). 1

Critical Threshold

• Anti-HBs ≥10 mIU/mL = Immune and protected 2
• Anti-HBs <10 mIU/mL = Non-responder requiring revaccination 1

Important caveat: Different assays have different cutoff values, so refer to the specific test's package insert for accurate interpretation of anti-HBs levels. 1

Interpretation Algorithm

If Anti-HBs ≥10 mIU/mL:

• Immunocompetent persons: Consider immune with long-term protection; no further periodic testing needed 1, 2
• Immunocompromised persons: May require annual testing to assess antibody concentrations 1, 2

If Anti-HBs <10 mIU/mL After Primary Series:

1. Administer complete second vaccine series (all doses on appropriate schedule) 1
2. Retest anti-HBs 1-2 months after final dose of second series 1
3. If still <10 mIU/mL after two complete series: Test for HBsAg to rule out chronic infection 1, 2

Special Populations Requiring Different Approaches

Healthcare Personnel Previously Vaccinated

For HCP with documented complete vaccination but no prior postvaccination testing: 1

1. Measure anti-HBs
2. If <10 mIU/mL: Give 1 booster dose, retest in 1-2 months
3. If still <10 mIU/mL: Give 2 more doses, retest after completion
4. If persistently <10 mIU/mL: HCP needs hepatitis B evaluation for all future exposures

Immunocompromised Patients

• Annual anti-HBs monitoring is recommended to assess antibody concentrations 2
• Revaccinate when levels fall <10 mIU/mL 2

Hemodialysis Patients

• Annual monitoring with booster doses if anti-HBs falls below 10 mIU/mL 2

Common Pitfalls to Avoid

Do not test unvaccinated or incompletely vaccinated persons for anti-HBs as the ≥10 mIU/mL correlate of protection has only been validated for those who completed an approved vaccination series. 2

Timing matters: Testing too soon after vaccination (before 1 month) or too late (beyond 2 months) may yield misleading results. 1

Transient HBsAg positivity: Individuals may test positive for HBsAg 1-3 days following vaccination with recombinant hepatitis B vaccine, which resolves spontaneously and does not indicate infection. 3 This is why the 1-2 month window is critical.

Sex differences exist: Females demonstrate more rapid and robust responses to booster vaccination compared to males, which may influence interpretation in borderline cases. 4

When Prevaccination Testing Is Indicated

For certain high-risk groups, prevaccination testing should include anti-HBc, HBsAg, and anti-HBs: 2

• Household, sexual, or needle-sharing contacts of HBsAg-positive persons
• HIV-positive persons
• Persons born in high-endemic regions

Critical point: Serologic testing should not delay vaccination—administer the first vaccine dose immediately after collecting blood for testing. 1