Background/Purpose:

The live herpes zoster (HZ) vaccine is
effective in healthy older people to reduce the incidence and burden of HZ.  Recent
results from a long-term follow-up study of participants in the Shingles
Prevention Study trial has shown that its protection attenuates by 10 years. The
corresponding duration of protection afforded by vaccination for patients with
autoimmune or inflammatory (AI) diseases is unclear.

Methods:

Using Medicare from 2006-2012 for patients with
AI diseases, this retrospective cohort study identified  HZ vaccinated patients
who had no history of HZ before HZ vaccination, and had been continuously
enrolled in Medicare Parts A, B and D during the 12 months prior to HZ
vaccination (baseline) and throughout follow up. To control for confounding, patients
without HZ vaccination were matched 2:1 to those with HZ vaccination on year of
vaccination, age, gender, race, AI disease, biologic use, DMARDs and steroids. HZ
cases were defined as the presence of an HZ diagnostic code plus concomitant
anti-viral therapy. Follow up started one month after vaccination and ended at
the earliest date of: HZ, death, loss of Medicare coverage or Dec 31, 2012. Matched
patients were censored when vaccinated and then allowed to be included in the
vaccination group. We calculated HZ incidence rates (IRs) yearly and used Poisson
regression for repeated measures to calculate the adjusted risk ratio of HZ for
each year using the first year as the reference.

Results:

In
the AI cohort, 46.5% had rheumatoid arthritis, 31.7% psoriasis, 4.5% psoriatic
arthritis, 21.1% inflammatory bowel disease, and 1.4% ankylosing spondylitis.  Of
43,369 HZ vaccinated patients and 86,738 matched unvaccinated patients, we
identified 820 and 2,265 HZ events respectively. IRs among vaccinated increased
from 0.75 per 100 person years in the 1st year post vaccination to 1.36 in the
6^th year post (Figure). The HZ IRs among unvaccinated remained
steady through the 6 years. After multivariable adjustment, vaccinated patients
had significantly lower HZ risk compared to those not vaccinated in year 1 (RR
0.52, 95% CI 0.45-0.61), with waning protection over 5 years.  By year 6, no
significant protection against HZ was demonstrable (RR 0.92, CI: 0.45 – 1.86).

Conclusion:

HZ vaccine effectiveness decreased over time
among patients with autoimmune and inflammatory diseases. Protection related to
the live HZ vaccine appears to wane over 5 years, and re-vaccination might be considered
at that time.

Figure:  Incidence rate (IR) and
95% Confidence Interval for herpes zoster over time among patients who had HZ
vaccination compared to the matched patients not vaccinated.