Transmission of Variant Creutzfeldt-Jakob Disease Through Blood Transfusion and Plasma-Derived Products: A Narrative Review of Observed and Modeled Risks.

Secondary transmission of variant Creutzfeldt-Jakob disease (vCJD) can occur through blood transfusion or receipt of plasma-derived products. However, published reviews on this topic are outdated, focused on a single country or product type, or did not comprehensively review modeling studies on the risk of transfusion-transmission. We reviewed existing data on observed and modeled risks of transfusion-transmission of vCJD. To date, five patients are suspected to have acquired clinical vCJD or a vCJD infection after receiving a blood or plasma-derived product from a donor who later developed clinical vCJD. All of these cases received a nonleukodepleted blood-derived product in the United Kingdom between 1994 and 1999. Thus, all transfusion-associated cases occurred before the adoption of universal leukodepletion in 1999, which supports the preferential tropism of vCJD for leukocytes. In descriptive cohort studies, no cases of clinical vCJD were observed over ∼13 years of follow-up. In modeling studies, the risk of collecting a contaminated donation was generally <23 per million donations, that of infection was generally <10 per million transfusions or doses, and that of clinical vCJD was generally <2 per million transfusions or doses. These low risk estimates and the two-decade long absence of new cases of transfusion-associated vCJD suggest vCJD poses minimal risks to the safety of the blood supply. Furthermore, despite concerns of a second wave driven by individuals harboring a non-MM genotype at codon 129 of PRNP, there has been only 1 autopsy-confirmed case of clinical vCJD in an MV individual in 2016. The current trend to reassess or (in some countries) fully withdraw the blood donation criteria related to vCJD therefore seems justified, safe, and may significantly expand the donor base.