Just Give the Second Dose
You do not need to restart the Twinrix series—simply continue with the second dose now, followed by the third dose. The ACIP guidelines explicitly state that interrupted hepatitis B vaccination schedules do not need to be restarted 1.
Key Principle: Never Restart an Interrupted Series
The 2022 ACIP recommendations are crystal clear on this point: "If the HepB vaccination schedule is interrupted, the series does not need to be restarted" 1. This applies directly to Twinrix, which follows a standard 3-dose schedule at 0,1, and 6 months 2.
What You Should Do Now
- Give the second dose immediately (no matter how much time has elapsed since the first dose)
- Schedule the third dose at least 8 weeks after this second dose
- Ensure the third dose is given at least 16 weeks after the original first dose 1
Why This Works
The first dose you received has already primed your immune system. Research demonstrates that even with prolonged intervals, the immune system retains memory of the initial vaccination 3. When you receive the second dose, you'll mount a robust secondary (anamnestic) response, with studies showing geometric mean titers of 1103-2538 mIU/mL after delayed second doses 3.
Common Pitfall to Avoid
Do not restart the series. Restarting wastes vaccine doses and delays completion of protection. The minimum interval between doses 2 and 3 is 8 weeks, and the final dose must be at least 16 weeks from the first dose 1. Doses given ≤4 days before the minimum interval are considered valid, but earlier doses should be repeated 1.
Expected Protection
After completing all three doses (even with delays), you should achieve: