» Hepatitis B Virus Vaccine Inactivated is a sterile preparation consisting of a suspension of particles of Hepatitis B surface antigen (HBsAg) isolated from the plasma of HBsAg carriers; treated with pepsin at pH 2, 8 M urea, and 1:4,000 formalin so as to inactivate any hepatitis B virus and any representative viruses from all known virus groups that may be present; purified by ultracentrifugation and biochemical procedures and standardized to a concentration of 35 µg to 55 µg of Lowry (HBsAg) protein per mL. The preparation is adsorbed on aluminum hydroxide and diluted to a concentration of 20 µg Lowry protein per mL or other appropriate concentration, depending on the intended use. The Vaccine meets the requirements for potency in animal tests using mice and by a quantitative parallel line radioimmunoassay. It contains not more than 0.62 mg of aluminum per mL and not more than 0.02 percent of residual free formaldehyde. It contains thimerosal as a preservative. It meets the requirements of the tests for pyrogen and for general safety (see Safety Tests—General under Biological Reactivity Tests, In Vivo 88).