Vaccination: a new option to reduce the burden of herpes zoster

Abstract

There is a strong correlation between the incidence of herpes zoster (HZ) and increasing age, with a marked rise in incidence from approximately the age of 50-60 years. The lifetime risk is approximately 25% and the disease is associated with acute and sometimes persistent pain, which substantially reduces the day-to-day functioning and quality of life of affected individuals, particularly older adults. The disease most commonly occurs as a result of an age-related decline in cell-mediated immunity. A live attenuated zoster vaccine has been developed to boost the varicella-zoster virus-specific cell-mediated immunity of older adults and, via this mechanism, protect the individual against HZ and its complications. Evidence that the vaccine is effective in older patients comes from the pivotal Shingles Prevention Study. This was a randomized, double-blind, placebo-controlled trial involving approximately 40,000 adults aged 60 years or more. The HZ vaccinated group had a 51% lower incidence of HZ, a 67% reduction in postherpetic neuralgia (defined as pain rated at three or more on a scale ranging from zero [no pain] to ten [pain as bad as you can imagine], persisting or occurring 3 months or more after rash onset), and a 61% lower burden of illness (a composite measure of the incidence, severity and duration of pain and discomfort caused by HZ), indicating that the vaccine decreased both the incidence of HZ and the average severity of HZ in vaccinees who developed HZ. Moreover, there was a 73% reduction in the number of cases of HZ with severe and long-lasting pain. Overall, the vaccine was well-tolerated with the most common adverse events being mild injection site reactions and headache. A continuation trial from the Shingles Prevention Study involving over 14,000 patients approximately 7000 in the HZ vaccine and placebo groups) confirmed that the efficacy of vaccination against HZ is durable through 7 years in terms of a significantly reduced incidence of HZ, a reduced incidence of postherpetic neuralgia and a markedly lower burden of illness. Although significant improvements have been made, available treatment options are only partially effective, and once postherpetic neuralgia is established, management is difficult. Therefore, the introduction of the zoster vaccine is a promising strategy to reduce morbidity associated with HZ, a particular concern in older adults.