A huge £80-million clean-up operation to cut the risk from blood infected with CJD was announced in Britain yesterday.
In future white blood cells, which theoretically could harbour the agent that transmits the disease, will have to be filtered out of all donated blood. But critics maintain that the process, leucodepletion, is not efficient enough to ensure that all blood used in transfusions is safe.
The government was urged to take the decision by the Spongiform Encephalopathy Advisory Committee (SEAC). Since November, SEAC scientists have been assessing the CJD blood risk. During this time, contingency plans for a leucodepletion programme were drawn up in case the threat proved real.
SEAC has now told the government that the risk, although small, is serious enough to warrant action. The move will add £80 million to the £70 million-a-year already being spent to protect plasma-based blood products, used to treat haemophiliacs, burns victims and people with weak immune systems, from new variant CJD.
In May the government ruled that all plasma must be imported from outside Britain. The decision came after advice from the Committee on Safety of Medicines two months earlier.
Blood products were thought to pose a significant risk because they are made from plasma collected from thousands of different donors.
Scientists now think that if any CJD infectious agents exist in human blood they are most likely to be found in the white blood cells called lymphocytes. These are produced in the lymph glands and are a vital part of the immune system.
According to one estimate one in 125 transfusion patients could be at risk from blood contaminated with the new strain of CJD.
The Deputy Chief Medical Officer, Dr Jeremy Metters, stressed that the move was a "purely precautionary measure". He added: "Leucodepletion will be rolled out in a systematic way, so that blood supplies are not interrupted and patients will continue to get blood when they need it."