Yes, we have seen the Canadian guidelines for the shingles vaccine and we have discussed it several times in many of our answers.
In fact, we referenced it heavily our answer to this recent question:
You are correct in stating that the Canadian immunization guidelines recommend waiting at least one year from your last episode of shingles to be immunized with the vaccine.
The following is an excerpt from those guidelines:
"For adults ≥50 years of age without contraindications who have had a previous episode of HZ [herpes zoster], immunization with a 2 dose series of RZV [Shingrix] should be offered. Immunization with RZV [Shingrix] may be considered at least one year after the episode of HZ [herpes zoster]. Persons with active HZ [herpes zoster] should not be immunized with HZ [herpes zoster] vaccine."
It should be noted that this recommendation differs from the one given by the CDC (Centers for Disease Control) and ACIP (Advisory Committee on Immunization Practices) in the United States.
They state that you simply should not receive the vaccine if you have an active shingles infection. They don't recommend any waiting period after an active infection has resolved, however. Per the CDC:
"If a patient is experiencing an episode of herpes zoster, vaccination should be delayed until the acute stage of the illness is over and symptoms abate."
Difference In Recommendation
Why do the Canadian guidelines and the CDC differ in their recommendation in regard to a waiting interval between a shingles infection and getting vaccinated?
It seems to be based on each organization's philosophy of how they make their medical recommendations based on the available evidence.
We do know that individuals are still at risk for a shingles infection, even if they have had an episode before. What we don't know is if there is a 'best' time to get vaccinated after having one.
This is due to the lack of studies discussing the potential risks and benefits of receiving the vaccination respective to the time you last experienced a shingles episode.
There are no studies to suggest that a waiting interval is necessary, but then again, there aren't any studies either showing getting immunized soon after an episode puts you at more risk of side effects (or decreased vaccine efficacy).
So basically, we don't know if there is an added risk or benefit in regard to timing.
In fact, the Canadian guidelines clearly state that there is insufficient evidence for their recommendation. Instead, it is based on 'expert opinion'.
"NACI [National Advisory Committee on Immunization] concludes that there is insufficient evidence to recommend an interval between previous episode of HZ and vaccination with RZV [Shingrix] (Grade I Evidence). Therefore this recommended interval is based on expert opinion."
Reading through much of the available evidence, it appears that the Canadian guidelines suggest a year interval for a few reasons, including:
- There is a lack of safety data available regarding receiving the vaccine within a year of having an active infection.
- There is a low risk of a recurrent episode one year after having an active infection anyway.
Overall, since there is a low risk of a recurrent shingles episode, they are erring on the side of caution.
The CDC in the United States is taking the position that since there aren't studies suggesting that it is unsafe to get vaccinated within a year of an infection, they simply recommend to get it after the infection has cleared since you can get shingles more than once.
Studies on the matter are inconclusive.
For example, one study, published in The Journal of Infectious Diseases, reviewed medical records of individuals who received the shingles vaccine between 180-730 days after infection and those who didn't.
They found that those vaccinated had a lower incidence of recurrent shingles infections than those who did not, but only by a very small percentage (in fact, it was not 'statistically significant').
The study concluded that since the risk of a recurrent episode is so low, more studies are needed to decide whether or not it is necessary to immediately vaccinate after an episode has cleared (and if it is safe to do so).
As discussed above, there certainly is a difference in the recommendations from the CDC (United States) and NACI (Canada).
The difference is not due, however, to a supposed lack in efficacy from vaccinating too soon after a shingles episode.
It is more based on the lack of safety studies and whether or not there is an added benefit.
I hope this answer helps!
The CDC (Centers for Disease Control) in the United States doesn't recommend a waiting interval between an active shingles infection and getting the shingles vaccine. They simply recommend to wait until the active infection clears. The NACI [National Advisory Committee on Immunization] in Canada, on the other hand, recommends to wait one year between experiencing an active shingles infection and getting the vaccine. The difference in recommendations is mostly based on the lack of available safety data and questions as to whether or not receiving the vaccination soon after an episode confers a significant added benefit versus waiting.
- Recommendations of the Advisory Committee on Immunization Practices for Use of Herpes Zoster Vaccines. CDC
- Herpes Zoster (Shingles) Vaccine: Canadian Immunization Guide. Canada.ca
- Updated Recommendations on the Use of Herpes Zoster Vaccines. Canada.ca
- Update on the Use of Herpes Zoster Vaccine. Canada.ca
- Herpes zoster vaccine and the incidence of recurrent herpes zoster in an immunocompetent elderly population. PubMed