Fig. 2

Comparison of recruitment rates between re-randomization and parallel-group designs in trials of asthma exacerbations. *PG parallel-group, RR re-randomization. The red line denotes recruitment for a parallel-group trial. The blue line denotes recruitment for a re-randomization trial where each participant may be enrolled for a maximum of two treatment episodes. The green line denotes recruitment for a re-randomization design where each participant may be enrolled for a maximum of four treatment episodes. The dotted line denotes the sample size target. Panel a denotes a small trial (n = 508) with a short recruitment duration (27 months). Panel b denotes a small trial (n = 508) with a long recruitment duration (47 months). Panel c denotes a large trial (n = 1200) with a short recruitment duration (27 months). Panel d denotes a large trial (n = 1200) with a long recruitment duration (47 months)