Residual risk of transfusion-transmitted human immunodeficiency virus, hepatitis C virus, and hepatitis B virus infections in Italy

Background: Estimating the risk of transfusion-transmitted infections (TTIs) is essential for monitoring blood safety. The residual risk of TTI was estimated for nearly 90 percent of the blood supply in Italy. Study Design and Methods: Data were analyzed from 1,079,281 repeat donors, corresponding to 5,361,000 donations made in blood transfusion centers throughout Italy in the period 1999 through 2001. The residual risk of transfusion-transmitted human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections was estimated with the incidence rate-window period model. The denominator for the incidence rate (i.e., the number of person-years at risk) was estimated on a sample of 5850 donors. Results: The risk of an infectious donation entering the blood supply, per 1 million donations, was 1.91 (probable range, 0.52-3.32) for HIV, 16.74 (9.57-24.01) for HCV, and 69.16 (43.12-102.70) for total HBV (adjusted for vaccination and hepatitis B surface antigen transience). Conclusions: In Italy, the estimated residual risk of TTI is apparently low, particularly for HIV infection. Although the estimated risks are higher for HCV and HBV, the introduction of mandatory viral detection tests for HCV in 2002 should account for an 80 percent reduction in the HCV risk. Moreover, the ongoing HBV vaccination program will contribute to reducing the risk of transfusion-transmitted HBV.