Elle asked
I received the 2nd dose of Shingrix 6 weeks after 1st. The nurse at doctor's office scheduled saying must take it from 6-8 weeks after the 1st. I had chills and fever for 2 days. No side effects with 1st dose though. Now after Googling, I see that the time frame is really 2-6 months. Did I get so sick because it was too soon? Will I still be fully covered ?
At a glance
- Shingrix is given in two doses. The recommended dosing schedule is for the first dose to be given initially, followed by a second dose administered anytime between 2 and 6 months later. However, the Advisory Committee on Immunization Practices (ACIP) states that the minimum interval between doses Shingrix is 4 weeks. It is unknown whether or not receiving the second dose prior to 2 months (8 weeks) decreases effectiveness or increases side effects. If the second dose is given less than 4 weeks after the first dose, the second dose should be repeated.
Answer
You are correct that the second Shingrix dose is to be administered 2 to 6 months after getting the first dose according to the Centers for Disease Control.
This administration schedule, like most vaccines, was determined mostly from data obtained from clinical trials for the vaccine.
In fact, according to the study published in the journal Vaccine, three different dosing schedules were tested for Shingrix:
- Two doses, with the second dose being administered 2 months after the first (i.e. 0-2).
- Two doses, with the second dose being administered 6 months after the first (i.e. 0-6)
- Two doses, with the second dose being administered 12 months after the first (i.e. 0-12)
The results of the study concluded that the '0-2' dosing schedule and the '0-6' dosing schedule were 'non-inferior', a statistical term meaning that both schedules are considered to be as effective as one another (within a given deviation).
The '0-12' dosing schedule did not demonstrate 'non-inferiority' to the other two which is why Shingrix is only recommended to be dosed 2-6 months after the first dose.
Unfortunately, there have been no studies completed testing whether or not Shingrix loses effectiveness, or if there is an increased risk of side effects if the second dose is given too soon.
Nevertheless, there certainly is a concern that not following the recommended wait time between doses could cause it to be less effective when it comes to preventing shingles.
The Centers for Disease Control has a fairly extensive practice guideline covering vaccine schedules and minimum dosing intervals. They state that getting doses too close together could result in a reduced immune response:
"In clinical practice, vaccine doses occasionally are administered at intervals less than the minimum interval or at ages younger than the minimum age. Doses administered too close together or at too young an age can lead to a suboptimal immune response."
Although there are no studies that evaluated whether or not getting the second dose of Shingrix too soon reduces immune response, the Advisory Committee on Immunization Practices recommends the following:
References
- ^ Immunogenicity, reactogenicity and safety of 2 doses of an adjuvanted herpes zoster subunit vaccine administered 2, 6 or 12 months apart in older adults: Results of a phase III, randomized, open-label, multicenter study. ScienceDirect
- ^ Timing and Spacing of Immunobiologics. CDC
- ^ Recommendations of the Advisory Committee on Immunization Practices for Use of Herpes Zoster Vaccines. CDC
