If an adult has received only the first dose of the recombinant zoster vaccine (Shingrix) and missed the second dose for several months, should the series be restarted or can the second dose be given alone?

Shingrix Series Continuation After Delayed Second Dose

If you have received only the first dose of Shingrix and missed the second dose for several months, you do not need to restart the series—simply give the second dose as soon as possible. 1, 2

Evidence-Based Recommendation

The CDC explicitly states that there is no maximum interval after the first dose; you should complete the series with a single second dose regardless of how much time has elapsed. 1, 2 This guidance applies whether the delay has been months or even years.

Key Supporting Evidence

• The recommended interval between doses is 2-6 months, with a minimum interval of 4 weeks. 1, 2
• If the second dose is administered beyond 6 months, effectiveness is not impaired—real-world data from a large Medicare cohort study showed that second doses given at ≥180 days maintained full effectiveness with no significant reduction in vaccine performance. 3
• The guideline explicitly instructs: if a dose is administered too soon (before 4 weeks), repeat that dose; however, no instruction exists to repeat doses given too late, confirming that delayed doses remain valid. 1

Real-World Completion Data

• Among U.S. adults who received the first dose, approximately 70% completed the two-dose series within 6 months and 80% within 12 months, demonstrating that delayed completion is common and accepted in clinical practice. 4, 5
• The two-dose vaccine effectiveness was 70.1% in real-world studies, significantly higher than the 56.9% effectiveness of a single dose, underscoring the importance of completing the series rather than restarting. 3

Clinical Algorithm

1. Verify first dose administration: Confirm the patient received the first Shingrix dose (not Zostavax).
2. Administer second dose immediately: Schedule and give the second dose at the next available appointment, regardless of the interval since the first dose. 1, 2
3. Do not restart the series: There is no clinical or immunologic rationale to repeat the first dose. 1, 2
4. Document completion: Record the series as complete after the second dose.

Common Pitfalls to Avoid

• Do not confuse Shingrix dosing intervals with other vaccines that require series restart after prolonged delays—Shingrix has no maximum interval. 1, 2
• Do not order serologic testing to determine if the first dose "still counts"—antibody titers do not guide zoster vaccination decisions, and testing would only delay protective vaccination. 2
• Do not give a third dose thinking the patient needs to "catch up"—only two doses total are required for the complete series. 1, 2
• Avoid missed opportunities: If the patient presents for any healthcare visit, administer the second dose rather than scheduling a future appointment, as 96% of patients who received only one dose had subsequent healthcare visits where the second dose could have been given. 5

Special Considerations

• For immunocompromised adults aged ≥18 years, the preferred interval is shorter (1-2 months between doses), but the same principle applies: delayed second doses do not require series restart. 1, 2
• If the patient is starting immunosuppressive therapy, prioritize completing the second dose before initiation when feasible, but do not delay necessary treatment. 1