Website of the Department of Health

Risk assessments for vCJD and blood transfusion

From the first identification of vCJD as a new disease, risk assessments carried out within the Department of Health (DH) were based on the presumption that infection might be transmissible from person to person. Models were developed to assess the risks of such secondary transmission, given that an unknown number of people might be carrying vCJD without showing any symptoms of the disease.

The two most significant potential routes were identified as blood transfusion and hospital surgery. Work on surgery can be accessed at elsewhere in this section and is discussed further in Bennett et al (2005). This page introduces a pair of papers concerned with possible vCJD transmission via donated blood, both produced by analysts within the Economics and Operational Research (EOR) Division of DH.

Both papers were discussed by the relevant scientific advisory committees during 2002, and have informed the further precautions taken since then. The aim of placing them in the public domain is to put the risk assessments underlying policy more fully on record, and to expose the methods used to wider scrutiny and review. Both papers are reproduced as presented in 2002, except for the addition of some clearly-identified footnotes drawing attention to new scientific evidence, precautionary measures introduced in the meantime, or other relevant developments. The preface also outlines these subsequent developments, and the extent to which these confirm or change the 2002 analysis. Further discussion of the role played by risk assessment in this area can be found in Bennett and Dobra (2006).

Given the many uncertainties, DH risk assessments for vCJD transmission have all used a scenario-based approach, considering wide ranges of assumptions rather than attempting to make predictions. Aside from the prevalence of vCJD infection amongst donors, the risk of blood-borne transmission will clearly depend on whether blood taken from a donor incubating vCJD can transmit infection. At the time these papers were produced, there was no direct evidence even on this basic point, though it is now established beyond reasonable doubt, as discussed in the preface.

Throughout, the aim has been to arrive at conclusions that are as robust as possible - roughly valid across a wide range of scenarios consistent with current evidence. One can then evaluate possible risk reduction measures as realistically as possible, using models "fit for purpose" in each case

The preface sets each of the two papers in context, and then provides a brief summary of subsequent developments.

• Download preface (PDF, 91K)
• Exclusion of blood component recipients from donation: the impact on potential vCJD transmission risks
• On vCJD transmission through blood components: reconciling modelled risks with case evidence