Variant Creutzfeldt-Jakob disease and the risks from blood transfusion (page 4 of 4)
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A study co-ordinated by the National CJD Surveillance Unit in Edinburgh has traced and followed up all individuals known to have received blood components donated by vCJD patients.4 As of 30 January 2006, 18 of the vCJD cases were known blood donors and could be traced to donation centres. Sixty-six components of blood were transfused from these patients to 66 named recipients, 26 of whom are currently alive.
Measures to reduce the risks from blood transfusion
Several measures have been put in place in the UK to reduce the risks from blood transfusion. From 1997 onwards, all probable vCJD cases have been reported to the National Blood Service and any remaining blood donated by the cases is destroyed. Between July 1998 and October 1999, leucodepletion was phased in; recent research has suggested that approximately 40% of infectivity is removed through this process,8 but the effect of lower infectivity on the risk of infection is unclear. From April 2004, recipients of blood transfusions received since 1980 in the UK have been excluded from donating blood. In August 2004, this was extended to exclude apheresis donors who were unsure about whether they have had a blood transfusion.
Other blood products
Blood, or its derivatives, are used in a number of other products including clotting factors for haemophilia patients. Whilst transmission via these other products has not yet been observed, the potential risks of acquiring infection similarly depend on the prevalence of infection in the population. One particular concern is that such products are derived from large ‘pooled’ donations and, as such, the potential for receiving infected blood could be much greater. To reduce these risks, between November 1998 and December 1999, UK-sourced plasma was phased out in the manufacture of blood products.
Summary
The incidence of vCJD has continued to decline from its peak in 2000. However, there remains substantial uncertainty about the number of people harbouring infection, with recent survey results suggesting approximately 3,800 infected individuals in the 10–30 age-group. The risks of transmission via blood transfusion depend on this underlying prevalence of infection and on the age-dependent patterns of blood donation and transfusion. Measures are currently in place to reduce this risk including leucodepletion and a ban on donating blood for those who have previously received a blood transfusion.
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