Continue Vemlidy Indefinitely
This patient should continue Vemlidy (tenofovir alafenamide) indefinitely, as he remains HBsAg-positive despite achieving viral suppression. The absence of anti-HBs is irrelevant to treatment decisions—what matters is that he has not achieved HBsAg loss, which is the only criterion that would allow consideration of stopping nucleos(t)ide analogue therapy 1.
Why Continue Treatment
HBsAg-Positive Status is the Key Determinant
The 2025 EASL guidelines are explicit: antiviral therapy with nucleos(t)ide analogues should only be stopped after confirmed HBsAg loss (with or without anti-HBs seroconversion) 1. Your patient remains HBsAg-positive, so stopping therapy is not appropriate regardless of:
- Undetectable HBV DNA (which he has achieved)
- Duration of viral suppression (4 years in this case)
- Anti-HBs status (which remains negative)
Anti-HBs is Not Required for Treatment Decisions
The guidelines specifically note that anti-HBs seroconversion is not significantly associated with the durability of HBsAg loss 1. In fact, among patients who achieve HBsAg loss:
- Only 38% had detectable anti-HBs titers in large Asian cohorts
- Anti-HBs seroconversion can take years: 58% at 5 years, 78% at 10 years after HBsAg loss 1
The FDA label for Vemlidy reinforces this, warning that discontinuation of anti-hepatitis B therapy may result in severe acute exacerbations of hepatitis B 2.
Expected Timeline for HBsAg Loss
Realistic Expectations
HBsAg loss with nucleos(t)ide analogue therapy is extremely rare and slow:
- Long-term data shows the median time to clear HBsAg is 52.2 years (range 30.8-142.7 years) even with sustained viral suppression 3
- The average HBsAg decline is only 0.084 log₁₀ IU/year during the undetectable HBV DNA phase 3
- Lifetime therapy is required in the vast majority of HBV-infected patients 3
Higher Rates in Special Populations
One exception: HIV/HBV coinfected patients show higher HBsAg loss rates (16% after median 8.4 years of tenofovir therapy), particularly those with low quantitative HBsAg (<1000 IU/mL) at treatment start 4. However, this patient appears to have HBV monoinfection.
Monitoring Strategy
While continuing Vemlidy, monitor:
Every 6-12 months:
- HBsAg quantitative levels (if available)—declining levels may predict eventual loss
- HBV DNA to confirm sustained suppression
- ALT/AST
- Renal function (creatinine, eGFR, urinalysis for proteinuria/glucosuria) 2
- In patients with chronic kidney disease: serum phosphorus 2
Annually:
- Hepatocellular carcinoma surveillance (ultrasound ± AFP) if indicated by age, cirrhosis status, or other risk factors
Safety Considerations
Vemlidy has demonstrated excellent long-term safety through 5 years:
- 85% maintained HBV DNA <29 IU/mL at year 5
- No resistance development
- Minimal renal impact (median eGFR decline <2.5 mL/min)
- Minimal bone density changes (<1% decline) 5
Critical Pitfall to Avoid
Do not stop Vemlidy based on undetectable HBV DNA alone. Research demonstrates that even patients with undetectable intrahepatic covalently closed circular DNA (cccDNA) experience virologic rebound after nucleos(t)ide analogue cessation—12 of 13 patients rebounded within 20 weeks 6. Your patient, who is still HBsAg-positive, has active infection and will almost certainly experience viral rebound with potential hepatic flare if therapy is discontinued.
Future Consideration for Stopping
The only scenario where stopping could be considered 1:
- Confirmed HBsAg loss on two occasions 6 months apart
- If cirrhosis is present: wait for anti-HBs seroconversion OR complete 12 months of consolidation therapy after HBsAg loss
- Close monitoring for at least several months after stopping (monthly ALT, HBV DNA, HBsAg for first 3-6 months, then every 3 months for at least 1 year) 2