Chickenpox is a highly contagious disease and is caused by the varicella-zoster virus (VZV). Following chickenpox, immunity is usually lifelong. Immunocompromised patients are at risk of infection following re-exposure to the virus. Shingles is a re-activation of varicella-zoster virus, which remains dormant in sensory-nerve ganglia after chickenpox. Chickenpox is a self-limiting disease in children that lasts about 4-5 days and is characterised by fever, malaise and generalised vesicular rash. More severe disease manifests in adolescents, adults and immunocompromised persons. These individuals are also at higher risk for complications such as varicella pneumonia; disseminated or haemorrhagic varicella.

The reactivation of the primary infection (chickenpox) later in life is termed herpes zoster (shingles). The chickenpox virus can hide from the immune system in nerves and when the immune system becomes suppressed (immunodeficiency; cancers; drugs) the virus reactivates. Shingles causes numbness, itching or severe pain with lesions in a strip like pattern normally on one side of the body.

Varicella-zoster immunoglobulin is used to prevent chickenpox in those patients who have no immunity to the virus and who are at risk for severe complications of chickenpox. It should be administered as soon as possible, but not more than 96 hours after exposure.

The decision to administer varicella-zoster immunoglobulin should be based on:
1. Whether the patient is susceptible

• An accurate immune history needs to be established. If the history is reliable, it is an accurate indicator of immunity. A negative history from a parent is more reliable than a self-reported negative history from an adult. The majority of adults with negative or uncertain histories are seropositive on serological testing.

2. Whether the exposure is likely to result in infection

• Continuous household contact
• Direct contact exposure (generally > 1 hour of direct contact while indoors)
• Hospital contact (in same two-four bed room or adjacent beds in a large ward or prolonged face-to-face contact with a infectious staff member)
• Newborn contact (newborn of mother who had onset of chickenpox 5 days or less before delivery or within 48 hours after delivery)

3. Whether the patient is at greater risk for complications than the general population.

• Premature neonates of less than 28 weeks gestation or with a birth weight of 1000 g or less, who have had exposure to the varicella-zoster virus
• Neonates if exposure to the varicella-zoster virus occurred 5 days or less before delivery or within 48 hours after delivery
• Bone marrow transplant recipients despite a history of chickenpox, who have had exposure to the varicella-zoster virus
• Immunocompromised patients, who have had exposure to the varicella-zoster virus, including:
  • Patients currently being treated with chemotherapy or generalised radiotherapy or within 6 months of terminating such therapy.
  • Patients who have received high dose steroids in the preceding 3 months
  • Symptomatic HIV-positive patients who have no history of chickenpox
  • Patients who have received an organ transplant and are currently on immunosuppressive treatment.

Varicella-zoster immunoglobulin is not indicated for adults and children who are immune. Although it may prevent infection in healthy children, it is not indicated, as the ensuing natural infection is usually mild. It is also not indicated for the treatment of clinical varicella (chickenpox) or herpes zoster (shingles), or for the prevention of disseminated zoster.

Varicella-zoster immunoglobulin can only be obtained with a doctor's prescription. Discuss with your doctor why it has been prescribed for you and the benefits and risks of this medicine.