Hepatitis B Surface Antibody Testing Frequency for PrEP Patients
For patients initiating or continuing HIV pre-exposure prophylaxis (PrEP), hepatitis B surface antibody (anti-HBs) should be tested only once at baseline as part of the initial hepatitis B screening panel, not routinely thereafter.
Initial Baseline Screening (One-Time Testing)
At PrEP initiation, order a complete hepatitis B panel including:
- Hepatitis B surface antigen (HBsAg)
- Hepatitis B core antibody (anti-HBc) total IgG or IgG
- Hepatitis B surface antibody (anti-HBs) 1
This three-test panel should be obtained before or at the beginning of PrEP therapy, but PrEP should not be delayed while awaiting results 1.
No Routine Follow-Up Anti-HBs Testing Required
Once baseline immunity is documented (anti-HBs ≥10 mIU/mL), no further periodic anti-HBs testing is needed in immunocompetent PrEP patients 2, 3. This is because:
- Immunocompetent individuals who achieve protective anti-HBs levels maintain lifelong protection through immune memory, even when antibody levels subsequently decline below 10 mIU/mL 2, 3
- Protection persists for at least 30 years among vaccine responders, and likely for life 4
- 88% of vaccinated individuals mount an anamnestic response when given a challenge dose 30 years after initial vaccination, demonstrating persistent immune memory 4
Management Based on Baseline Results
If Anti-HBs ≥10 mIU/mL at Baseline
- Document immunity and proceed with PrEP 2, 3
- No further anti-HBs testing needed 2, 3
- No booster doses required 2
If Anti-HBs <10 mIU/mL at Baseline
- Administer one booster dose of hepatitis B vaccine immediately 2, 4
- Retest anti-HBs 1-2 months after the booster dose 2, 4
- If anti-HBs remains <10 mIU/mL after booster, complete a full second 3-dose vaccine series 2, 4
- Retest 1-2 months after completing the second series 2
If HBsAg-Positive (Chronic HBV Infection)
- Refer for hepatology consultation 1
- Monitor ALT and HBV DNA at baseline and every 6 months during PrEP 1
- Consider antiviral prophylaxis with tenofovir-based regimens (which are also used for PrEP) 1
If HBsAg-Negative but Anti-HBc-Positive (Past HBV Exposure)
- For standard PrEP patients: monitor with HBsAg and ALT during treatment; start antiviral therapy only if HBV reactivation occurs 1
- No routine anti-HBs monitoring needed 1
Special Populations Requiring Different Monitoring
Annual anti-HBs testing with booster doses when levels fall <10 mIU/mL is required only for:
- Immunocompromised patients (HIV-infected persons, transplant recipients, those on chemotherapy) 2, 3, 4
- Hemodialysis patients 2, 3, 4
These patients cannot rely on immune memory alone and require maintained circulating antibody levels for protection 2.
Common Pitfalls to Avoid
- Do not routinely recheck anti-HBs years after vaccination in immunocompetent PrEP patients—waning antibodies are expected and do not indicate loss of protection 2, 3
- Do not interpret low anti-HBs levels measured years after childhood vaccination as non-response—these individuals retain immune memory 2
- Do not delay PrEP initiation while awaiting hepatitis B serologic results 1
- Do not test anti-HBs if hepatitis B immune globulin (HBIG) was given in the previous 3-4 months, as this interferes with accurate assessment 1, 4
Documentation
Maintain written, dated records of the baseline hepatitis B panel results and any subsequent vaccination doses administered 2.