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.

12th International Congress on Infectious Diseases

Lisbon, Portugal / June 15-18, 2006

After infection, the varicella virus is present in a latent form in nerve ganglia, where it may be reactivated at any time, although clinical herpes zoster (HZ) is much more likely to occur in individuals aged over 50 years. The most important complication associated with HZ is post-herpetic neuralgia (PHN), which is caused by nerve damage associated with the inflammatory response to virus. Ophthalmic zoster and involvement of the central nervous system are other less common but nevertheless serious complications associated with HZ. According to Dr. Biagio Pedalino, Lyon, France, “20% of HZ patients over 50 develop PHN and the lifetime risk of HZ is around 25%.” The associated pain is generally worse in older patients.

The Case for Prevention

Dr. Janet McElhaney, Allan M. McGavin Chair in Research and Head, Department of Geriatric Medicine, University of British Columbia, Vancouver, explained, “An increasing number of people are living to 80 years or more; often, however, these older subjects have to endure disability and chronic diseases that detract from their quality of life.” She also pointed out that older patients with underlying chronic but controlled diseases are at risk of progressing as a result of acute illness. In the case of PHN, excruciating pain often results in reduced activity, which in turn can quickly lead to reduced mobility and disability.

To illustrate this point, Dr. McElhaney discussed the case history of an 83-year-old woman who had a stroke that left her with left-sided weakness. After rehabilitation, her left-sided strength was improving and it looked like she would be able to return to her home but then she experienced pain. HZ was diagnosed after the appearance of rash and she received appropriate antiviral treatment. After the rash had remitted, PHN occurred. Pain medication was prescribed to manage her pain, but their use was limited by sedation. Her rehabilitation program was affected and her left-sided weakness re-emerged.

Dr. McElhaney concluded, “Although she recovered from her stroke, in the end she was unable to return to her home, and this was really due to a complication of shingles.” The case history is also an example of how PHN may arise even with appropriate antiviral treatment for HZ, strengthening the case for prevention.

Herpes Zoster Vaccination: Reducing the Burden of Illness

According to Dr. Robert Johnson, Consultant in Anesthesiology and Pain Medicine, University of Bristol, UK, after varicella, “Cell-based immunity declines with age, and at some point, usually decades after the primary infection, it drops below an arbitrary threshold.” The body is then unable to prevent the reactivated virus from replicating. Vaccination before immunity drops below this critical level should prevent the individual from possible reactivation.

The hypothesis was tested by the Shingles Prevention Study, a randomized, double-blind, placebo-controlled study in 38,546 immunocompetent adults aged 60 years or older (Oxman et al. N Engl J Med 2005;352(22):2271-84). Those in the active treatment arm received a 0.5 mL subcutaneous injection of live attenuated vaccine. Both treatment arms were well balanced in terms of baseline characteristics and underlying diseases.

The primary end point was relative efficacy at reducing burden of illness (BOI) caused by HZ, which was measured by the incidence, severity and duration of the pain. The incidence of PHN was the secondary end point. Patients were followed for HZ for 3.1 years. “One of the impressive aspects of the study was the remarkably low number of patients who did not complete follow-up: the number of patients in both arms completing the study was 95%,” Dr. Johnson commented.

Among patients in the treatment group, there was a 61.1% reduction (P<0.001) in BOI due to HZ, a 66.5% decrease (P<0.001) in the incidence of PHN and a 51.3% reduction in the incidence of HZ. According to Dr. Johnson, “Even when HZ was not prevented, the attenuation of the condition was sufficient to reduce the effect of PHN and BOI.” Researchers concluded that the use of the zoster vaccine demonstrated statistical significance among older adults in the reduction of morbidity from HZ and PHN.

Dr. Johnson also presented data from the safety substudy, which closely monitored a subgroup of patients for adverse effects and local effects. Complications were comparable in both groups except for local events such as itching and headaches reported more often in the vaccine group.

Polysaccharide Vaccines for Pneumococcal Disease

Pneumonia and influenza are the sixth most common cause of death among older individuals in the US. According to Dr. Christopher Ohl, Wake Forest University School of Medicine, Winston-Salem, North Carolina, “Thirty per cent to 50% of all cases of hospitalized pneumonia in the US are thought to be due to streptococcal pneumonia.”

Studies that confirm the efficacy of polysaccharide vaccines are difficult to carry out, although a large study published recently in patients hospitalized for community-acquired pneumonia showed that vaccination against pneumococcus was associated with improved survival (Fisman et al. Clin Infect Dis 2006;42(8):1093-101). “Taken together,” noted Dr. Ohl, “these studies show that the polysaccharide vaccine is effective at preventing bacteremic or invasive pneumococcal disease.”

The goal in the US for 2010 is to have vaccinated more than 90% of people aged 65 years or over. However, Dr. Richard Zimmerman, University of Pittsburgh School of Medicine, Pennsylvania, reported that “the coverage among this population has plateaued at less 60%” and that “61% to 62% of patients in a study admitted to hospital for pneumonia had not been vaccinated despite admission to hospital in the preceding five years.”

He remarked, “Hospitalization represents an opportunity to think about vaccination.” He went over institutional protocols that could encourage vaccination of high-risk patients. These include standing orders to automatically vaccinate such patients, provided there are no contraindications. The results of a study in a hospital where these protocols had been implemented provided support for the protocol in that the number of patients admitted for pneumonia was reduced after its implementation. Dr. Zimmerman added that computer-based recording can also help keep track of those who have not been vaccinated.

It is often unclear when an individual should be revaccinated. According to recommendations from the Centers for Disease Control and Prevention in the US, revaccination is advisable after at least five years in adults aged 65 years or other patients with certain long-term health problems and risk factors (e.g. situations associated with immunodepression). Revaccination is not associated with systemic effects, although local injection-site reactions seem to occur more frequently.

Summary

Researchers here agreed that vaccination of adults, and particularly older individuals, is beneficial. A large, well-conducted study has shown that HZ vaccination can help prevent the disease and its consequences. This is particularly important, given that pain due to PHN can be particularly debilitating and difficult to treat because of the patient characteristics. Polysaccharide vaccination against pneumococcal disease is known to be effective, yet vaccination programs could still be more extensively implemented.