Vaccines and Preventable Diseases:
Varicella Vaccine - Q&A about High Risk
Recommendations for Postexposure Prophylaxis of Varicella for Persons at High Risk for Severe Disease - Clinical Q&A
What is recommended for prophylaxis following varicella exposures among persons without evidence of immunity who are at high risk for severe disease?
For healthy adolescents and adults (persons aged 13 years or older) without evidence of immunity, vaccination within 3-5 days of exposure to rash is beneficial in preventing or modifying varicella. Studies have shown that vaccination administered within 3 days of exposure to rash is 90% or more effective in preventing varicella while vaccination within 5 days of exposure to rash is approximately 70% effective in preventing varicella and 100% effective in modifying severe disease.
For persons without evidence of immunity who have contraindications for vaccination but are at risk for severe disease and complications, use of varicella zoster immune globulin (VZIG) is recommended for postexposure prophylaxis.
What are the indications for VZIG use?
The Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) indicate that the decision to administer VZIG to a person exposed to varicella-zoster virus (VZV) should be based on whether a) the patient lacks evidence of immunity (either by having no evidence of prior infection or by lacking documentation of vaccination), b) the exposure is likely to result in infection, and c) the patient is at increased risk for severe disease and complications compared to the general population. (www.cdc.gov/mmwr/preview/mmwrhtml/00042990.htm).
Both healthy and immunocompromised children and adults who have verified positive histories of varicella (except for bone-marrow transplant recipients) can be considered immune (see evidence of immunity). Persons who have received bone-marrow transplants should be considered non-immune, regardless of prior history of varicella or varicella vaccination in themselves or in their donors. However, bone-marrow recipients who develop varicella or herpes zoster following transplantation should subsequently be considered immune.
VZIG is not indicated for persons who received 2 dose of varicella vaccine and became immunocompromised due to disease or treatment later in life. These persons should be closely monitored, and, if disease develops, treatment with acyclovir should be instituted at the earliest signs or symptoms.
Several types of exposure can place susceptible persons at risk for varicella. Direct contact exposure is defined as more than 1 hour of direct contact with an infectious person while indoors; substantial exposure for hospital contacts consists of sharing the same hospital room with an infectious patient or having prolonged, direct, face-to-face contact with an infectious person (e.g., healthcare workers). Brief contacts with an infectious person (e.g., contact with x-ray technicians or housekeeping personnel) are less likely to result in VZV transmission than are more prolonged contacts.
Persons at greater risk for severe varicella who have contraindications for vaccination and for whom VZIG is recommended include:
- Immunocompromised persons, including persons who have primary and acquired immunodeficiency disorders, neoplastic diseases, and are receiving immunosuppressive treatment. Patients receiving monthly high-dose immune globulin intravenous (IGIV) (400 mg/kg or greater) are likely to be protected and probably do not require VZIG, if the last dose of IGIV was given less than 3 weeks before exposure (Red Book, American Academy of Pediatrics)
- Neonates whose mothers have signs and symptoms of varicella from 5 days before to 2 days after delivery
- Premature neonates exposed to varicella postnatally
- Those born at or after 28 weeks of gestation whose mothers do not have evidence of immunity should receive VZIG because the infant’s immune system may not be fully functional.
- Those who are less than 28 weeks gestation or who weigh 1,000g or less at birth should receive VZIG regardless of maternal history because such infants may have not acquired maternal antibodies.
- Pregnant women without evidence of immunity
When should VZIG be administered?
VZIG provides maximum benefit when administered as soon as possible after exposure, but it may be effective if administered as late as 96 hours after exposure. Effectiveness of VZIG administered more than 96 hours after exposure has not been evaluated and is of uncertain value.
What is the recommended dosage?
The recommended dose is 125 U/10kg (22 lbs) of body weight, up to a maximum of 625 U. VZIG should be administered intramuscularly as directed by the manufacturer.
How can I obtain VZIG for a patient in need?
The product currently used in the United States, VariZIG™ (Cangene Corporation, Winnipeg, Canada), is available under an Investigational New Drug application protocol and may become licensed in the future (www.fda.gov/cber/infosheets/mphvzig020806.htm). VariZIG is a lyophilized presentation which, when properly reconstituted, is approximately a 5% solution of IgG that can be administered intramuscularly. VariZIG can be obtained from the sole authorized U.S. distributor, FFF Enterprises (Temecula, California) (24-hour telephone, 800-843-7477, www.fffenterprises.com (exit)). FFF Enterprises delivers VariZIG on an as needed basis (e.g., when there is an identified exposed person for whom VZIG is indicated). Under normal circumstances, the distributor delivers the vaccine within 24 hours of request.
Additional information on VZIG use can be found in the 1996 ACIP recommendations for prevention of varicella (MMWR 1996;45:20-24; www.cdc.gov/mmwr/preview/mmwrhtml/00042990.htm).
Detailed information regarding how to obtain VariZIG can be found at: www.cdc.gov/mmwr/preview/mmwrhtml/mm5508a5.htm (MMWR 2006:55(08);209-210).
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Content last reviewed on May 29, 2007
Content Source: National Center for Immunization and Respiratory Diseases