Nat. Med. 14, 1333–1342 (2008); published online 23 November 2008; corrected after print 7 January 2009

In the version of this article initially published, the x-axis title of the right-hand graph in the 'Day 2' part of Figure 1f was incorrect. The title should read 'Time to death in secondary transplants (d)'. The error has been corrected in the HTML and PDF versions of the article.