Shingles Vaccine for Older Adults
A Vaccine to Prevent Herpes Zoster and Postherpetic Neuralgia in Older Adults. Oxman MN, Levin MJ, Johnson GR, et al. New England Journal of Medicine 2005;352(22):2271-2284.
Explanatory note: Varicella (chickenpox) is an infection caused by the varicella-zoster virus (VZV). VZV typically occurs during childhood (chickenpox) and remains in the body for life. In the elderly, the dormant virus may reappear as shingles (herpes zoster), typically beginning with burning pain developing into clusters of skin lesions. Almost half of the elderly with shingles develop complications; the most frequent complication is postherpetic neuralgia (PHN), a painful condition that affects the nerves despite resolution of the shingles skin lesions.
Does vaccination with a live attenuated VZV vaccine decrease the incidence and/or severity of herpes zoster and postherpetic neuralgia in adults 60 years of age or older?
The researchers conducted a randomized, double-blind, placebo-controlled trial with 38,546 adults 60 years of age or older. Participants were divided into two groups; one received an investigational VZV vaccine and the other a placebo. The participants were followed up for a median of 3 years to detect cases of shingles.
Once cases were identified, the researchers measured the severity and duration of herpes zoster, impact of herpes zoster on quality of life, and occurrence of PHN. Adverse events were measured for all patients during the study. In addition, an adverse events’ substudy of approximately three thousand patients from each of the placebo and vaccine groups was asked to measure daily temperatures and maintain a log of symptoms for the first 42 days after vaccination. Hospitalizations were also compared for the adverse events’ substudy, whereas deaths were measured for all study patients.
During the study period, a total of 957 confirmed cases of shingles were confirmed: 315 among vaccine recipients and 642 among placebo recipients. Also, there were 107 cases of postherpetic neuralgia: 27 among vaccine recipients and 80 among placebo recipients.
The zoster vaccine reduced the burden of illness—described by the severity and the duration of pain in patients who developed zoster—due to shingles among people 60 years of age or older by 61.1%. The vaccine reduced the overall incidence of shingles by 51.3% and the incidence of postherpetic neuralgia by 66.5%.
Mild adverse events such as redness or pain at the injection site were observed in the vaccine group, but number of hospitalizations did not differ in the substudy.
The relevance/bottom line
The investigational live attenuated VZV vaccine was effective in reducing the morbidity of shingles (herpes zoster) and its most common complication, PHN, in older adults. Deaths and hospitalizations did not differ between groups and adverse events were mild in the vaccine group.
The primary difference between the investigational VZV vaccine for older adults and the currently licensed VZV vaccine targeted to children is the increased potency of the vaccine for older adults, required to stimulate an adequate immune response.
This vaccine would protect older adults from recurrence of an infection with high morbidity at a time when natural exposure (“booster”) to VZV has been reduced by childhood immunization. It is important to note, however, that recent evidence suggests that there has been no significant change in the age-adjusted incidence of herpes zoster (shingles) since introduction of the VZV vaccine for children in 1995.
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