Reports

This report is based on medical evidence presented at sanctioned medical congress, from peer reviewed literature or opinion provided by a qualified healthcare practitioner. The consumption of the information contained within this report is intended for qualified Canadian healthcare practitioners only.

45th Annual Meeting of the Infectious Diseases Society of America

San Diego, California / October 4-7, 2007

Each year in the US, there are an estimated 556,200 episodes of herpes zoster (HZ) in individuals ³60 years of age. Approximately 69,600 cases of post-herpetic neuralgia (PHN) lasting more than 90 days, the most serious consequence of HZ infection, occur each year in the same age cohort. Antiviral therapy can shorten the duration of HZ infection and reduce the severity of the disease but even early initiation of antiviral therapy does not prevent PHN, as discussed by Dr. Michael Oxman, Professor of Medicine and Pathology, University of California, San Diego. “If patients do develop PHN, therapies for it are not very satisfactory and they are particularly difficult to use in the older age group,” he told delegates.

Shingles Prevention Study Findings

Thus, a highly compelling argument can be made that prevention of HZ and its attendant complications would have a significant impact on the health of older individuals. Indeed, evidence from the SPS (Shingles Prevention Study) strongly support the benefit of vaccinating adults ³60 years of age, for whom the vaccine is currently recommended.

As reviewed by Dr. Oxman, results from the SPS showed that the vaccine reduced the burden of illness (BOI) by 61.1% in all participants compared with placebo. The BOI was a composite measure of the incidence, severity and duration of total pain and discomfort caused by HZ. Vaccine efficacy was very similar for those between the ages of 60 and 69 years, where a single dose of the vaccine reduced the BOI by 65.5% over placebo. In participants ³70 years of age, the vaccine reduced the BOI by 55.4%, again relative to placebo. Perhaps most importantly, “the vaccine exceeded our best expectations” when it came to reducing the incidence of PHN, Dr. Oxman reported. In this regard, its efficacy was undiminished by age, where it reduced the incidence of PHN by 66.5% in the overall cohort, by 65.7% in those between the ages of 60 and 69 years and by 66.8% in those ³70 years of age, he observed.

Investigators also analyzed the effect of the vaccine on individuals with a severity of illness score of over 600—“more than 60 days of the worst pain you can imagine,” Dr. Oxman indicated—as well as its effect in individuals with a score of more than 800, “or 80 days of the worst imaginable pain.” In both younger and older patients, the vaccine reduced the most severe illness by >80% and there was a shift to less severe disease among those who developed HZ infection in the vaccine group as well. The incidence of serious adverse events was the same between vaccine and placebo groups, and the vaccine was well tolerated.

As a consequence of the SPS findings, the US Food and Drug Administration licensed the use of the HZ vaccine for adults ³60 years of age. This was followed by a recommendation from the Advisory Committee on Immunization Practices (ACIP) who seconded this, regardless of whether or not adults reported a prior episode of HZ. It is well established that an episode of HZ will boost immunity against subsequent infection. However, as Dr. Oxman pointed out, “We do not know how quickly that boost decays and how quickly patients become vulnerable to HZ again,” therefore, the ACIP felt that patients needed to be protected against HZ reactivation regardless of prior infection.

Widespread Uptake

Extrapolating from the SPS findings, researchers calculated that if every individual in the US ³60 years of age received the vaccine, 283,700 cases of HZ a year would be prevented, as would 46,400 cases of PHN lasting for >90 days. This does not mean that all cases of HZ nor all cases of PHN would be eliminated, Dr. Oxman cautioned. Nevertheless, the public health implications of widespread uptake of HZ vaccination are evident based on numbers alone.

Dr. Oxman also addressed the issue of how physicians could capitalize on the inherent benefits of vaccinating their older patients against HZ infection. Proponents of vaccination repeatedly emphasize that almost every medical encounter should be regarded as an opportunity to immunize their patients against preventable infections. For example, the influenza vaccine is universally recommended for older adults. As Dr. Oxman suggested, physicians can give the influenza vaccine in one arm and the HZ in the other, knowing that the immune response to both vaccines will be as robust as if the vaccines are given four weeks apart, with no increase in adverse events. Physicians may also want to consider giving the vaccine prior to any immunosuppressive intervention, as the probability that the HZ virus will be reactivated in immunosuppressed patients is very high. At the same time, “the likelihood that patients would be able to transmit the vaccine virus to others is close to nil,” Dr. Oxman reassured delegates.

In a separate study, Dr. Myron Levin, Professor of Pediatrics and Medicine, University of Colorado Health Sciences Center, Denver, and colleagues demonstrated that patients between the ages of 21 and 59 years experience the pain and discomfort of HZ just as acutely as those ³60 years of age. Dr. Levin and colleagues assessed the impact of HZ on a validated pain score—the Zoster Brief Pain Inventory score—as well as on activities of daily living (ADL) according to age.

During the first week following HZ onset, the mean pain score in patients between the ages of 21 and 59 years of age was 6.4, precisely the same score that was reported by patients ³60 years of age also during the first week of onset. The impact of the illness on ADL was also almost identical for both age groups, at 3.7 for the younger age group and 3.8 for those ³60 years of age. The study also showed that the percentage of patients who reported significant pain six weeks after rash onset increased with age, from 8% for patients between 21 to 49 years, to 16% for those between the ages of 50 and 59 years, to 22% for those aged ³60 years. Older adults also had lower varicella zoster virus-specific cellular immunity than younger patients at baseline but the boosting effect of the HZ episode itself was “substantial” for all age groups.

“People in the younger age group had just as much trouble with this disease as those in the older age group and for this reason, maybe we should be thinking about taking the use of this vaccine down to the age of 50, especially since many 50-year-olds are working,” Dr. Levin suggested.