Immunization can significantly lower the risk of serious complications from shingles among older adults, suggest findings from a new study published in Clinical Infectious Diseases and available online. Drawing on data from approximately 2 million Medicare beneficiaries from 2007 to 2014, the retrospective cohort study evaluated the effectiveness and durability of the currently available, but under-utilized, vaccine.
Shingles, or herpes zoster, is a painful skin condition that occurs when the varicella-zoster virus, the same virus that causes chickenpox, is reactivated later in life in nerve cells. Almost one out of every three people in the United States will develop shingles during their lifetime. Because the incidence increases with age, seniors are particularly at risk. A live-attenuated vaccine, ZOSTAVAX®, was first licensed in the U.S. in 2006, after a clinical trial showed an overall 51 percent reduction in shingles incidence among patients aged 60 years or older.
The new study results suggest that the vaccine is most effective against severe cases of shingles requiring hospitalization, as well as postherpetic neuralgia, a less common but serious complication of the virus which causes chronic pain. For preventing hospitalized cases of shingles, the virus showed 74 percent effectiveness in the first three years and 55 percent effectiveness after four or more years had passed since vaccination. Vaccine effectiveness against postherpetic neuralgia was 57 percent in the first three years after vaccination and 45 percent in the years that followed.
"The fact that we found relatively high effectiveness against serious outcomes, such as hospitalization and postherpetic neuralgic, and that protection from these outcomes was sustained over time, adds to the considerable evidence that the vaccine is beneficial and that seniors should be encouraged to be vaccinated in higher numbers than what is happening currently," said study author Hector S. Izurieta, MD, MPH, of the Food and Drug Administration's Center for Biologics Evaluation and Research. The shingles vaccine is recommended in the U.S. for people 60 and older, but, in 2014, just 28 percent of adults in this demographic reported having received the vaccine, according to the Centers for Disease Control and Prevention.
The study found little evidence to suggest that protection from shingles varied among different age groups within the study population, although the vaccine's effectiveness declined over time. Protection against less serious cases of shingles not needing hospitalization was also considerably lower than protection against hospitalized cases and instances of postherpetic neuralgia.
In an editorial commentary published with the study, Steven Black, MD, of Cincinnati Children's Hospital, noted the efficacy of the authors' approach, stressing the likelihood that the study's results "most accurately reflect the impact of the vaccine in the Medicare population and, as almost all individuals over 65 years of age in the United States are enrolled in Medicare...the true effectiveness in seniors in the United States overall." "Until other vaccine regimens and newer vaccines are evaluated," Dr. Black wrote in his commentary, "it makes sense to continue with the current vaccination regimen to prevent a less than optimal but significant number of cases of the more serious complications."
Dr. Izurieta called the study's findings reassuring but acknowledged the potential for more accurate and comprehensive studies in the future. "Better methods should be developed to control for bias in the analysis of observational studies, particularly when less severe outcomes, such as community herpes zoster, are considered," he said.
Articles: Effectiveness and Duration of Protection Provided by the Live-attenuated Herpes Zoster Vaccine in the Medicare Population Ages 65 Years and Older, Hector S. Izurieta, Michael Wernecke, Jeffrey Kelman, Sarah Wong, Richard Forshee, Douglas Pratt, Yun Lu, Qin Sun, Christopher Jankosky, Philip Krause, Chris Worrall, Tom MaCurdy, Rafael Harpaz, Clinical Infectious Diseases, doi: 10.1093/cid/ciw854, published 27 February 2017.