I Forgot My Second Dose Of Shingrix And It's Been Over 3 Years

Answer

The recommendation from the CDC (Centers for Disease Control) and Immunize.org (formally Immunization Action Coalition (IAC)) is that even if more than 6 months have passed since your first dose of Shingrix, you should not restart the series. You should get the second dose whenever you are able to.

Shingrix Dosing Recommendations

Shingrix is an FDA-approved vaccine for preventing shingles and is a two-dose series. The second dose of Shingrix should be given 2 to 6 months after you received the first dose.

Although I talk about this more in the next sections, the safety and efficacy of getting Shingrix outside of the recommended dosing schedule has not been appropriately evaluated.

What If You Waited Longer Than Six Months?

If you waited longer than 6 months between doses, as mentioned, it is recommended to simply get the second dose whenever you can. Do not restart the series. Per the CDC:

Q: What should I do if a patient waits longer than 6 months to get the second dose?
A: You should give the second dose as soon as possible. However, you do not need to restart the vaccine series.

Per Immunize.org:

Q: My clinic cannot consistently keep Shingrix in stock due to high demand. How should we handle challenges ensuring patients receive a second dose?
A: Clinicians and patients should make every effort to ensure that two doses of Shingrix are administered within the recommended interval of 2 to 6 months. If more than 6 months have elapsed since the first dose of Shingrix, administer the second dose when possible. Do not restart the vaccine series.

Canadian health guidelines have the same recommendation. The following is from ImmunizeBC:

Q: It's been more than six months since my first dose of Shingrix®. Is it too late to get the second shot? Do I have to restart my vaccine series?
A: When more than six months have passed since your first Shingrix® vaccination, you should get the second dose as soon as possible. You do not need to restart the vaccine series—two doses of Shingrix® ensure optimal protection.

Are You As Protected From Shingles If The Second Dose Is Given More Than 6 Months After The First Dose?

Although we have some preliminary data on how well a two-dose series of Shingrix works if not given during the recommended dosing schedule, we don't have conclusive information.

The CDC itself states that our understanding of the effectiveness and safety of alternative dosing regimens is limited and an individual might remain at risk for shingles if you waited longer than the recommended interval between doses 1 and 2.

There is at least one study that I know of that has evaluated the efficacy of a non-standard dosing schedule.

One such study, which can be found here, evaluated a 0,12-month dosing schedule (i.e., getting your second dose of Shingrix 12 months after the first dose).

While the study did find a significant immune response in most individuals, (as measured by anti-gE geometric concentrations), there were a small number of participants that had a very low response, which caused the study to find that the 0,12-month dosing schedule was not 'non-inferior' to the 0,2-month dosing schedule.

In other words, the data from the 0,12-month dosing schedule wasn't within an acceptable range for an immune response when compared to the other, recommended dosing schedules.

There is no data that I could find that has evaluated the time gap you mentioned in your question, unfortunately, (greater than 3 years since your first dose).

So, overall, it appears you will certainly have some immune response to the second dose of Shingrix if it is given outside the recommended dosage window, but we don't, unfortunately, know how effective it will be and how that effectiveness compares to getting the vaccine within the recommended window.

Final Words

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