Viral safety of plasma-derived factor VIII and IX concentrates.

Treatment, or prevention, of bleeding in severe haemophilia requires lifelong therapy with repeated injections of factor VIII/IX concentrate which carry a risk of viral infection. The overall safety of all blood products depends not only upon careful donor selection and the screening of donations for infectious viruses, but also on the efficacy of specific anti-viral steps in the manufacturing process. As a result of the episodes of virus transmission by currently available concentrates there have been calls for all manufacturing processes to include two viral inactivation procedures. There have been no clinical studies, however, to demonstrate that these products have enhanced viral safety. A variety of other virucidal techniques are under evaluation. The way forward may be a form of post-marketing surveillance or pharmacovigilance in which large numbers of haemophiliacs are routinely screened for known transmissible viruses and the data systematically collected. It would probably be necessary to have a multinational arrangement because of the rarity of the transmission episodes. Such a system could also provide quick early warning of a difficulty with an individual product.