Date	Event	Description
12 January 2017	New search has been performed	Two new trials have been added to the review (SIT 2014; TWiTCH 2016). One trial, previously listed in 'Ongoing studies' has been moved to 'Excluded studies' (SCATE 2015).
12 January 2017	New citation required but conclusions have not changed	This update has included GRADE assessment of the quality of the evidence.
13 November 2014	New search has been performed	A search of the Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register identified: three additional references to the SWiTCH study (SWiTCH 2012); one additional reference to the STOP trial; two references reporting on both the STOP and the STOP II trials (STOP 1998; STOP 2 2005); and one additional reference to the ongoing SIT trial (SIT 2014).
6 November 2013	New citation required but conclusions have not changed	The inclusion of additional trials resulted in only minor amendments to the conclusion section of the review.
6 November 2013	New search has been performed	A Search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register identified six additional references to two already included trials (STOP 1998; STOP 2 2005) and 11 additional references to two trials previously listed in Ongoing studies (SIT 2014; SWiTCH 2012). The SWiTCH 2012 trial has now been listed as an included study. Two further studies have been included in the ongoing studies section of the review (SCATE 2015; TWiTCH 2016). The title has been amended to include the terms 'primary and secondary'.
22 May 2009	New search has been performed	A search of the Group's Trials Register did not identify any new references which may have been eligible for inclusion in this review.
31 July 2008	Amended	Converted to new review format.
31 July 2008	New search has been performed	A search of the Group's Haemoglobinopathies Trials Register identified no new trials potentially eligible for inclusion in the review.
1 August 2007	New search has been performed	A search of the Trials Register identified a total of 10 new references. Eight were of the STOP trials (two of which refer to both the STOP 1998 and STOP 2 2005 trials and so appear in both lists (Adamkiewicz 2006; Kwiatkowski 2002)): six new references to the STOP trial (STOP 1998) as follows (Adamkiewicz 2006; Kwiatkowski 2002; Kwiatkowski 2006; Lee 2006; Lezcano 2006; Wang 2005). The search also identified a further two abstracts (DeBaun 2005; Ware 2006) which have been listed in the 'Ongoing studies' section of the review.
1 February 2006	New search has been performed	A search of the Trials Register identified seven new references to the included trial (STOP 1998) as follows: Abboud 2004; Adams 2004; Bulas 2000; Gates 2002; Hsu 2003; Kwiatkowski 2002; Kwiatkowski 2003. It has also been reported that the STOP 2 2005 trial has been terminated early, although published findings are not yet available.
31 August 2004	New search has been performed	A search of the trials register identified no new trials eligible for inclusion in the review.
31 August 2003	New search has been performed	Additional references to the already included STOP 1998 study have been added. However, no new data have been found. The references added to the STOP 1998 study ID were: Adams 1998 Wang 1998 Adams 2002 Files 2002
30 September 2002	New search has been performed	Additional references to the already included STOP 1998 study have been added. Therefore, further results are presented on the following outcomes ‐ 1. Transfusion related complications 2. Incidence of transient ischaemic attack or silent infarction 3. Incidence of other sickle cell complications The references added to the STOP 1998 study ID were: Abbound 1999 Adams 1996 Adams 1997 Adams 1999 ‐ two references Adams 2001 Duncan 1997 Kutlar 2000 Lee 2002 Nichols 2001 Miller 2000 ‐ two references Miller 2001 Pegelow 1999 Pegelow 2001 Vichinsky 1999 Vichinsky 2001