By Richard R. Watkins, MD, MS, FACP
Associate Professor of Internal Medicine, Northeast Ohio Medical University; Division of Infectious Diseases, Cleveland Clinic Akron General Medical Center, Akron, OH
SYNOPSIS: A Kaiser Permanente-funded observational study of southern California residents demonstrated that the zoster vaccine has short term benefits in reducing the risk of shingles, but the effectiveness wanes significantly over time in elderly patients.
SOURCE: Tseng HF, Harpaz R, Luo Y, et al. Declining effectiveness of herpes zoster vaccine in adults aged ≥ 60 years. Clin Infect Dis 2016;213:1872-1875.
Since 2006 it has been standard clinical procedure to provide the herpes zoster (HZ) vaccine to the elderly (age 60 and older), as per guidelines published that year by the Advisory Committee on Immunization Practices. Despite these recommendations, evidence from subsequent research endeavors have cast serious doubts on the long-term efficacy of the shingles vaccine. As such, Tseng, et al. enacted a large, observational study designed to discern the efficacy of the HZ vaccine in protecting elderly (age 60 and older) adults from contracting shingles.
The participants in the study were all members of Kaiser Permanente Southern California, identified by their medical records. The study’s design called for two cohorts, the first being elderly members vaccinated between 2007 and 2014, and the second being randomly sampled, unvaccinated members, matched in a 3:1 ratio with vaccinated members of similar demographics for comparison. Criteria for exclusion were prior episodes of HZ within the previous year, demonstrated immune compromise like HIV infection, or prior use of immunosuppressive agents within the previous year. In final analysis the vaccine’s efficacy was estimated in follow-up years with the 1-adjusted hazard ratio.
The group that received vaccines contained 176,078 participants while the non-vaccine group had 528,234. The rate of HZ the vaccinated cohort was 8.0 cases/1,000 person-years, while the rate was 14.4/1,000 person-years in the unvaccinated cohort. Though vaccination was associated with a reduction in risk of HZ, the effectiveness of the vaccine declined after each year of follow-up: at the end of the first year the vaccine was 68.7% effective; however, by the eighth and final year of follow-up, the effectiveness had dwindled to just 4.2%. Over the eight years of the study, vaccinated participants had a cumulative risk of 7.0% of contracting HZ, while the cumulative risk was 10.5% in the unvaccinated cohort.