If Giulivi means that there are no reported cases of CJD or vCJD that have been transmitted through the blood supply, then he is right. But this lack of evidence does not mean that such transmission is not occurring. 1 Science is more than epidemiology.
Biology is complex, messy and richly various, like real life.
Spongiform encephalopathies occur in a wide variety of animals. So it is unlikely that CJD is transmitted through the blood supply. So it is really important to know if vCJD can be spread through the blood supply. Waiting for human epidemiologic evidence would be a mistake. Here is a possible biological mechanism that would allow prions attached to leukocytes to cross the blood brain barrier.