Herpes Zoster Vaccine Reduces Risk in Older Adults
Herpes zoster (also known as shingles) is a vesicular rash caused by reactivation of varicella zoster virus. The rash is painful and often disabling, and sometimes persists for months or years, a complication known as postherpetic neuralgia. There are approximately 1 million episodes of herpes zoster each year in the United States.
In 2006, following the Shingles Prevention Study (SPS), the US Food and Drug Administration licensed Merck & Co to manufacture Zostavax, a live zoster vaccine. The SPS trial included 38,546 participants ≥60 years of age with no history of herpes zoster. The vaccine reduced the incidence of herpes zoster and postherpetic neuralgia by 51% (P<.001) and 67% (P<.001). According to researchers, although the data showed the efficacy of the vaccine, confirmation of the results in field conditions is needed to confirm the ability to generalize the benefits of the vaccine to conditions of clinical practice.
To evaluate the risk of herpes zoster after herpes zoster vaccination, the researchers conducted a retrospective cohort study from January 1, 2007, through December 31, 2009. The primary study outcome was the incidence of herpes zoster. They reported study results in the Journal of the American Medical Association [2011;305(2):160-166]. The study included data from members of Kaiser Permanente, Southern California (KPSC). The vaccinated cohort included 75,761 members who received herpes zoster vaccine at ≥60 years of age from January 1, 2007, through June 30, 2009. Those members were matched 1:3 with 227,283 unvaccinated individuals; matching was accomplished based on birth date. Participants in both cohorts had continuous KPSC membership and drug benefits for the year prior to their index date. They were observed for the first occurrence of herpes zoster, termination of KPSC membership, or study completion.
Compared with the unvaccinated cohort, members in the vaccinated cohort were more likely to be white, female, and to have had a large number of outpatient visits, fewer visits to emergency departments, and fewer hospitalizations in the 12 months prior to the index date; the vaccinated cohort also had a lower prevalence of chronic diseases; P<.001 for all variables except age, which was the matching factor. Among members in the vaccinated cohort, the number of herpes zoster cases was 828 in 130,415 person-years compared with 4606 in 355,659 person-years in the unvaccinated cohort. Follow-up averaged 1.72 and 1.56 years in the vaccinated and unvaccinated groups, respectively. In univariate analysis, the incidence of herpes zoster was 6.4 per 1000 person-years (95% confidence interval [CI], 5.9-6.8) in the vaccinated group compared with 13.0 per 1000 person-years (95% CI, 12.6-13.3) in the unvaccinated group (P<.001).
Several factors were variants in the incidence of herpes zoster in the unvaccinated cohort. Incidence increased with age (≥80 years of age vs 60-64 years of age: hazard ratio [HR], 1.45; 95% CI, 1.30-1.63), was lower in males (HR, 0.75; 95% CI, 0.70-0.79), and lower in members who were black (HR, 0.69; 95% CI, 0.62-0.76). Incidence also varied by chronic disease: it was higher in members with lung disease (HR, 1.34; 95% CI, 1.13-1.59) than in those without lung disease. Other differences, including among members with kidney disease and heart disease, were not statistically significant. The differences in incidence persisted after adjusting for sex, race, chronic diseases, and use of healthcare. In summary, the researchers noted that “among immunocompetent community-dwelling adults aged ≥60 years, receipt of the herpes zoster vaccine was associated with a lower incidence of herpes zoster. The risk was reduced among all age strata and among individuals with chronic diseases.”
