Zoster vaccine (Zostavax) is a new preventative immunization for herpes zoster (HZ or shingles) in adults 60 years of age or older. The vaccine is prepared from a live, attenuated strain of varicella-zoster virus (VZV). Zostavax is designed to yield a more potent, higher titer than varicella virus live vaccine (Varivax), used in children for chicken pox.1
Shingles is caused by a reactivation of VZV, the virus responsible for chicken pox as a primary infection. Following resolution of the primary infection, the virus lies dormant in dorsal root and/or cranial nerve ganglia until it is reactivated. Shingles generally present as unilateral, painful, vesicular eruptions distributed along cutaneous dermatome paths. After resolution of the acute infection, scarring, postherpetic neuralgia (PHN), and other lasting effects can remain. Serious complications of HZ can include bacterial superinfection, nerve palsies, encephalitis, visual impairment, hearing loss, and death.1
The efficacy of Zostavax was evaluated in the Shingles Prevention Study (SPS), a double-blind, placebo-controlled study in which 35,546 subjects were randomized to receive either a single Zostavax dose (n = 19,270) or placebo (n = 19,276).3 All subjects were 60 years of age or older, but immunocompromised patients or those with a history of HZ were excluded. Study participants were followed from 31 days to 4.9 years (mean 3.1 years) for the development of HZ. Cases of HZ more than doubled in those receiving placebo when compared with those who had received Zostavax.1 The efficacy of the vaccine increased with decreasing age. Additionally, those that were vaccinated but still acquired HZ were 39% less likely to develop PHN than those given placebo.3
Indications
The Food and Drug Administration approved Zostavax in May 2006. In October 2006, the Centers for Disease Control and Prevention further recommended Zostavax for routine vaccination in patients over 60 years of age. Confirmation of previous chicken pox infection by serology is not necessary.4 Zostavax should not be used for the treatment of patients with current HZ or PHN. The new vaccine is not a substitute for varicella virus live vaccine and should not be used in children.2
Mechanism of Action
Reactivation of the varicella virus appears to be related to a decline in VZV-specific immunity. This can be due to a general immunosuppressed state or the naturally waning general immunity associated with aging. Zostavax works by specifically boosting the VZV immunity.3 There is no current data on specific drug interactions and drug metabolism is not relevant for this vaccine.
Contraindications
The vaccine is contraindicated for patients with any sensitivity to the drug or its components. The provider should screen potential vaccine recipients for the specific contraindications listed below.
* A history of anaphylactic/anaphylactoid reactions to gelatin, neomycin, or any other component of the vaccine.
* A history of primary or acquired immunodeficiency states including leukemia, lymphomas of any type, malignant neoplasms affecting the bone marrow or lymphatic system, or infection with HIV.
* Anybody on immunosuppressive therapy or high-dose corticosteroids.
* Those with active, untreated tuberculosis.
* Those who are or may be pregnant.2
Adverse Reactions
The SPS study used vaccination report cards over a 42-day postvaccination period to determine adverse effects. Injection site reactions were 48% in the Zostavax population compared to 17% in those who received placebo. All injection site reactions were considered mild and included, in order of decreasing prevalence, erythema, pain/tenderness, swelling, pruritus, warmth, and hematoma.3
Serious adverse effects, death incidence, and elevated temperature were no higher in those vaccinated compared to placebo (1.4%). The following were reported to be more common in Zostavax subjects over placebo but were reported in less than 2% of the study subjects: respiratory infection/disorder, fever, flu syndrome, diarrhea, rhinitis, skin disorder, and asthenia.3
When using any live, attenuated virus like Zostavax, immunosuppressed patients may experience a more extensive vaccine-associated rash or disseminated disease. However, this phenomenon has not been clinically evaluated in such patients or in those using topical, inhaled, or low-dose oral corticosteroid therapy.2
Dosage and Administration
Zostavax is administered subcutaneously and should not be given intravascularly. A single dose is given after reconstitution with the provided sterile diluent. To avoid affecting vaccine potency, only preservative and antiseptic-free syringes should be used.2
Zostavax should be stored frozen at an average temperature of -15 [masculine ordinal indicator]C (5 [masculine ordinal indicator]F) or colder.2 The diluent may be stored at room temperature. The vaccine should be used immediately after reconstitution to minimize any loss of potency and discarded if not used within 30 minutes. The reconstituted mixture should not be frozen.
Special Considerations
As with any vaccine administration, adequate treatment provisions for dealing with anaphylactic/anaphylactoid reactions (including epinephrine injection) should be readily available. The provider may decide to defer vaccination in those with an acute illness or fever. The SPS data were based on a 4-year follow-up and duration of protection is undetermined. Therefore, Zostavax may not provide complete protection in some patients. The effect of concurrent administration of Zostavax and antiviral medications or other vaccines has not been evaluated in clinical studies. Those without history of HSV infection may be vaccinated despite their exclusion from the SPS.4 One dose is immunogenic even in those without a confirmed antibody serostatus. Transmission of the virus after simple vaccination has not been studied, although those with a postvaccination rash may be contagious (see Sidebar: "Recommended Vaccines for Adults 50 Years of Age or Older").
Zostavax reimbursement is covered under Medicare Part D. Because provider offices are considered out-of-network under Medicare Part D, vaccination charges will be reimbursed under the out-of-network access rules. The cost is approximately $150 and patients currently must pay up-front and fill out a form to receive direct reimbursement from either private insurance or Medicare Part D. Many providers would like to see the vaccine included in the Part B fees; this continues to be a point of discussion for the Centers for Medicare and Medicaid Services.4
The U.S. Department of Health and Human Services has established a Vaccine Adverse Event Reporting System (VAERS) to accept all reports of suspected adverse events after the administration of any vaccine. The VAERS toll-free number is 1-800-822-7967. Adverse effects related to vaccinations may be reported on the paper form or submitted through the online system at https://secure.vaers.org/VaersDataEntryintro.htm.
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