Correction to: Gene Therapy, advance online publication, 12 November 2009; doi10.1038/gt.2009.148

The authors have discovered an error that they would like to correct. References 19 and 33 have been switched in the reference section.

Reference 19 should have been Mingozzi et al., Hum Gene Ther 2008; 19: 1090, and reference 33 should have been Mingozzi et al., Blood 2007; 1010: 2334–2341.

The authors apologize for this error.