Feasibility study
Prior to the initiation of STRIDES, a feasibility study was conducted in five blood donation sites (comprising 3 donor centres and 2 mobile teams) over a period of 15 weeks (25 March 2019 to 26 June 2019) to establish if the protocol for a cluster-randomised trial could be implemented successfully without disrupting routine blood collections. The feasibility study was also used to assess the acceptability of the interventions by blood donors. It showed that the implementation of the four different interventions under evaluation here−either individually or in combination−was practical and did not adversely affect routine blood collection (Supplementary Fig. 