»Varicella-Zoster Immune Globulin conforms to the regulations of the FDAconcerning biologics (see Biologics á1041ñ).It is a sterile 15percent to 18percent solution of pH7.0containing the globulin fraction of human plasma consisting of not less than 99percent of immunoglobulin Gwith traces of immunoglobulin Aand immunoglobulin M,in 0.3Mglycine as a stabilizer and 1:10,000thimerosal as a preservative.It is derived from adult human plasma selected for high titers of varicella-zoster antibodies.Each unit of blood or plasma has been found nonreactive for hepatitis Bsurface antigen by a suitable method.The proteins of the plasma pools are fractionated by the cold ethanol precipitation method.The content of specific antibody is not less than 125units,deliverable from a vial containing not more than 2.5mLsolution.The unit is defined as equivalent to 0.01mLof a Varicella-Zoster Immune Globulin lot found effective in clinical trials and used as a reference for potency determinations,based on a fluorescent-antibody membrane antigen (FAMA)method for antibody titration.