Who gets the best protection from Zostavax and how long does it last? Is that enough?
In a previous article Zoster Vaccine Quiz: How are We Doing? I talked about the value, and also some of the weaknesses, of the live attenuated vaccine Zostavax, the only vaccine currently available to help prevent herpes zoster (shingles) or post-herpetic neuralgia (PHN).
The incidence of shingles starts to climb rapidly after the age of 50; so, too, does the risk of getting PHN following an attack of zoster. So, what is the best age to give Zostavax? The answer partly depends on how long protection lasts.
How long does Zostavax provide good protection?
A. ≤3 years
B. ≤5 years
C. ≤7 years
D. ≤10 years
The correct answer is B. ≤5 years
Zostavax protection wanes within the first five years after vaccination. Thus, vaccine efficacy is higher in a person in their early 50's (say, 70%), but protection will be gone for the most part by age 60 when the risk of both zoster and PHN is higher. The experts at the CDC have decided that age 60 is the “sweet spot” for vaccine administration, but it won't be sweet for that person at age 70 who will be essentially unprotected 10 years after vaccine administration. Studies are underway looking at efficacy of a repeat Zostavax dose. But another option is being looked at that may make these studies moot.
Manufacturer Glaxo Smith Kline (GSK) may have an answer to the problem. The company is expected to file for approval later this year of a new vaccine to be named Shingrix. It is an inactivated vaccine containing a varicella antigen combined with an adjuvant that boosts the cell-mediated response immensely. Preliminary data show efficacy in the range of 91-97% across all age groups, including those over age 80. Duration of protection has not changed over 4 years, remaining in the 90%+ range. In comparison Zostavax protection is waning by 4 years post-vaccination, dropping from over 60% to a little over 40%. GSK has immunologic data going out about 6 years that looks at antibody specific C4 T cells, and the numbers are still high. They are also now looking at the use of this vaccine in immunodeficient populations for whom a live attenuated vaccine is contraindicated and in those who have previously received Zostavax. The vaccine is a two dose series.
I received a dose of Zostavax about 5 years ago, so I know my protection (about 65% at best) is now waning. I plan to be rolling my sleeve up once Shingrix becomes available.
CDC shingles surveillance page. http://www.cdc.gov/shingles/surveillance.html
This is a good general resource on Zostavax indications and efficacy. http://www.cdc.gov/vaccines/vpd-vac/shingles/hcp-vax-recs.html#effectiveness
Discusses the role of cell mediated immunity and shingles.http://www.ncbi.nlm.nih.gov/pubmed/19553630
Some slides looking at Shingrix by GSK. http://www.gsk.com/media/853396/randd-day-vaccines-session.pdf
FDA announcement reporting the good results so far on Shingrix. http://www.fdanews.com/articles/173843-gsks-shingrix-shows-positive-results-in-phase-3-trial