The US Food and Drug Administration (FDA) has approved Varizig for reducing the severity of chicken pox (varicella zoster virus) infections in high risk individuals when given within four days after exposure.

Varizig is a varicella zoster immune globulin preparation. Varicella zoster virus (VZV) causes chickenpox in children and shingles in adults. Varizig is the only FDA approved immune globulin for VZV after exposure available in the United States. It was designated as an orphan drug by the FDA and received a priority review.

Most people in the United States have immunity to VZV from vaccination or from having had chickenpox during childhood. However, people without immunity to VZV who are exposed to the virus may experience severe infections that are sometimes fatal.

People most at risk include children or adults with weakened immune systems, pregnant women, and infants exposed during pregnancy or after birth. Occasionally, healthy people without immunity to VZV may contract severe infections. Antiviral treatments are not always effective and cannot be used in some cases.

“This approval fills an unmet need by providing a treatment to lower the risk of severe, potentially fatal varicella infections in vulnerable patients,” said Karen Midthun, MD, director of the FDA’s Centre for Biologics Evaluation and Research.

Varizig is an antibody preparation manufactured from plasma of healthy donors with high anti-VZV antibody levels. The donated plasma comes from FDA-licensed collection facilities in the United States and Canada. Varizig is administered in two or more injections, depending on the weight of the recipient, within 96 hours after exposure. Varizig is approved for immuno-compromised children and adults, newborns, pregnant women, premature infants, children less than a year old, and adults with no immunity to VZV.

Varicella zoster immune globulin (VZIG) has been shown to lower the risk of severe infections if given soon enough after exposure. An earlier FDA-licensed VZIG was removed from the US market by the manufacturer in 2006, and Varizig has only been available under an investigational expanded access protocol during the licensing process.

In studies Varizig was shown to be comparable to VZIG and was as effective as VZIG in preventing infection during pregnancy. Data on Varizig collected from individuals treated under the expanded access protocol showed a low rate of severe VZV infection in susceptible individuals compared with the rate in untreated individuals.

The studies also showed that Varizig is safe for its intended use, with the most common side effects being pain at the injection site and headache.

Varizig is manufactured by Cangene Corporation in Winnipeg, Canada.