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Canada to Supply Varicella Postexposure Prophylaxis


 

The dwindling U.S. supply of varicella-zoster immune globulin has been replenished with a new unlicensed product made available under a Food and Drug Administration investigational new drug application, according to the Centers for Disease Control and Prevention.

An expanded access protocol for VariZIG (Cangene Corporation, Winnipeg, Canada) was granted in February as supplies of the only licensed U.S. varicella-zoster immune globulin (VZIG) product began to run out, following its discontinuation last October by the manufacturer, Public Health Biologic Laboratories of Boston.

VariZIG is intended for patients without evidence of immunity who have been exposed to varicella and who are at increased risk for severe disease and complications. The CDC's Advisory Committee on Immunization Practices recommends it for the following groups:

▸ Immunocompromised patients.

▸ Neonates whose mothers have signs and symptoms of varicella around the time of delivery (5 days before to 2 days after).

▸ Premature infants born at or after 28 weeks of gestation who are exposed during the neonatal period and whose mothers do not have evidence of immunity.

▸ Premature infants born before 28 weeks of gestation or who weigh 1,000 g or more at birth and were exposed during the neonatal period, regardless of maternal history of varicella disease or vaccination.

▸ Pregnant women.

The product is expected to provide maximum benefit when administered as soon as possible after exposure although it can still be effective if administered up to 96 hours after exposure (MMWR 2006; 55[earlyrelease]:www.cdc.gov/mmwr

For other patients not included in the above groups and without evidence of immunity, the varicella vaccine is recommended for prophylaxis within 96 hours and possibly up to 120 hours post exposure, according to the report.

The CDC recommends that health care providers “should make every effort to obtain and administer VariZIG” when indicated. It can be requested from the sole authorized U.S. distributor, FFF Enterprises (Temecula, Calif.), through its 24-hour telephone line, 800–843–7477.

The expanded access protocol received central institutional review board approval, meaning that the FDA does not require additional institutional review board approval at individual institutions, according to the CDC.

Pharmacists and health care providers who anticipate needing the product can acquire inventory in advance, and, as with any product used under an investigational new drug (IND) application, patients must be informed of its potential risks and benefits and must give their informed consent before using it.

Patients receiving the therapy should be observed closely for 28 days after exposure for signs and symptoms of varicella (VariZIG might prolong the incubation period by 1 week or more) and treated with acyclovir antiviral therapy if necessary.

When varicella vaccine is not contraindicated, patients receiving VariZIG should be subsequently vaccinated but only after a delay of 5 months.

Vaccination is not necessary if the patient contracts varicella after receiving VariZIG.

If VariZIG is not available within 96 hours of exposure, a single dose of immune globulin intravenous should be considered as an alternative, at a recommended dose of 400 mg/kg, administered once.

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