Quality and safety of human hepatitis B vaccine.

Preparation of hepatitis B vaccine in our laboratories consists of a series of steps that include initial concentration of surface antigen by ammonium sulfate precipitation, followed by isopycnic banding and rate zonal centrifugation in a K-II centrifuge. The partially purified antigen concentrate is digested with pepsin at pH2 and the antigen is unfolded in 8M urea solution followed by renaturation. After gel filtration, the antigen is treated with formalin in 1:4000 dilution, adsorbed onto alum, and preserved with thimerosal. The final product contains essentially pure hepatitis B surface antigen. The process relies both on physical elimination of infectious virus particles and treatment with highly viral-destructive reagents in the pepsin, urea and formalin steps. The process is known to be highly destructive of all known viruses tested and to include procedures that are known to be highly destructive of representatives of all known groups of animal viral agents. The three-step process in inactivation provides a fail-safe system for establishing safety of the product. Tests in more than 20'000 persons, who are under surveillance, have shown no untoward effect and have confirmed the safety of the product.