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Vaccination reduces severe herpes zoster complications in seniors
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An FDA study examining the efficacy of the currently available herpes zoster vaccine in Medicare beneficiaries showed that the vaccine was most effective against severe cases of herpes zoster, or shingles, that require hospitalization. The vaccine’s effectiveness and duration of protection, however, waned over time.
Zostavax (Merck), the live-attenuated herpes zoster (HZ) vaccine, was licensed in the U.S. in 2006 following the results of a clinical trial involving more than 38,000 participants that showed the vaccine reduced the incidence of HZ by 51%, according to Hector S. Izurieta, MD, MPH, of the FDA’s Center for Biologics Evaluation and Research, and colleagues. However, there are limited post-marketing data on the vaccine, and questions regarding its value remain.
Izurieta and colleagues launched a large, retrospective study using Medicare databases with information on approximately 2 million beneficiaries to further evaluate the effectiveness and duration of protection of the HZ vaccine in seniors aged 65 years or older. For the primary analysis, the researchers matched 945,992 vaccinated beneficiaries with 945,992 unvaccinated beneficiaries to compare their outcomes. A secondary analysis was conducted to determine HZ incidence and complications in 608,982 HZ-vaccinated participants and 608,982 matched participants who received the pneumococcal vaccine, Pneumovax 23 (23-valent pneumococcal polysaccharide vaccine, Merck; PPSV23), but not the HZ vaccine.
In the primary analysis, the researchers followed participants (median age, 77 years) for up to 7.5 years, during which 56,964 HZ cases were identified. After adjusting for HZ risk factors and other potential confounders, they determined that vaccine effectiveness (VE) for community HZ was 33% (95% CI, 32%-35%) in the first 3 years of follow-up and 19% (95% CI, 17%-22%) after 4 years or more of vaccination. The vaccine was more effective in preventing hospitalizations and postherpetic neuralgia (PHN), a serious complication of HZ that causes chronic pain. For hospitalized HZ, VE was 74% (95% CI, 67%-79%) for the first 3 years of follow-up and 55% (95% CI, 39%-67%) after 4 or more years. For PHN, VE was 57% (95% CI, 52%-61%) in the first 3 years and 45% (95% CI, 36%-53%) in the following years.
In the secondary analysis, VE for community HZ was slightly higher than in the primary analysis at 37% (95% CI, 36%-39%) after 3 years and 22% (95% CI, 20%-25%) in the following years. Other outcomes including HZ hospitalizations and PHN were comparable to those in the primary analysis.
Although previous data from the Shingles Prevention Study indicated that VE declines with age, Izurieta and colleagues found little evidence supporting that pattern. The researchers concluded that their findings provide additional evidence that the vaccine reduces HZ incidence and its complications when used in clinical practice.
“The fact that we found relatively high effectiveness against serious outcomes, such as hospitalization and postherpetic neuralgia, 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,” Izurieta said in a press release. “The shingles vaccine is recommended in the U.S. for people 60 and older, but, in 2014, just 28% of adults in this demographic reported having received the vaccine according to the Centers for Disease Control and Prevention.”
In a related commentary, Steven Black, MD, of Cincinnati Children’s Hospital, noted that the findings “most accurately reflect the impact of the vaccine in the Medicare population and ... the true effectiveness in seniors in the United States overall.”
“Given these results and the number of patients impacted, one can conservatively state that, especially for community zoster where the number of cases is high and for ophthalmic zoster where morbidity is high and incidence relatively high, that the protection provided by the current live-attenuated zoster vaccine is suboptimal,” he wrote. “Until other vaccine regimens and newer vaccines are evaluated, 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.” – by Stephanie Viguers
Disclosures: Black reports being a part-time consultant for GlaxoSmithKline and Merck vaccines. Izurieta and colleagues report no relevant financial disclosures.
Perspective
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The findings of the study of effectiveness of the live-attenuated herpes zoster vaccine for the prevention of herpes zoster or shingles in individuals older than 65 years of age published recently in Clinical Infectious Diseases are very encouraging. The study performed a retrospective cohort analysis of the Medicare database and included individuals 65 years of age or older followed from January 2007 through July 2014 who were and were not vaccinated with the live-attenuated herpes zoster vaccine and followed for the occurrence of shingles. Those who were included in the study had an average age of 77 years. The study reported that the vaccine effectiveness (VE) for the occurrence of shingles in individuals living in the community was 33% (95% CI: 32%–35%) and 19% (95% CI: 17%–22%), for the first 3, and subsequent 4+ years after vaccination, respectively. VE for the prevention of post-herpetic neuralgia was 57% (95% CI: 52%–61%) and 45% (95% CI: 36%–53%) in the first 3 and subsequent 4+ years, respectively. Finally, VE for hospitalization due to shingles was 74% (95% CI: 67%–79%) and 55% (95% CI: 39%–67%), in the first 3 and subsequent 4+ years, respectively. Differences in VE by age group were not significant.
These findings highlight that the vaccine provided protection against all forms of herpes zoster but that this protection declined with time after vaccination. The VE was also higher for the more severe manifestations of disease, including post-herpetic neuralgia and hospitalization for shingles. These findings support the routine administration of the vaccine for the prevention of herpes zoster in older adults.
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