130 Chapter 7 The median follow-up time before starting emicizumab was 56 (IQR 52–68 and range 12–166) weeks per individual. The individuals had a follow-up time of at least 1 year, except for four children who were less than a year old, who had 12–15 weeks, one 3-yearold child with 36 weeks, and one adolescent (age 14) with 47 weeks of follow-up time. Most PwHA (n = 97, 87%) were on FVIII prophylaxis before starting emicizumab therapy. The median prophylactic dose of the FVIII-SHL products was 44 units/kg/week and was higher for the FVIII-EHL products at 60 units/kg/week. Most of the adults received FVIIISHL prophylaxis, while most of the children received FVIII-EHL prophylaxis; five were PUPs, as demonstrated in Supplemental Table ST1. Emicizumab therapy The reasons for switching from the previous treatment to emicizumab were breakthrough bleeds/ineffectiveness (n = 34, 30%), difficult venous access (n = 34, 30%), userfriendliness/individual preference (n = 17, 15%), non-adherence (n = 12, 11%) or FVIIIinhibitor development (n = 10, 9%), additionally five individuals (4%) were PUPs. The reasons to start emicizumab according to age subgroup are represented in Supplement Table ST2. The median follow-up time during emicizumab therapy was 51 (IQR 29–75 and range 1–190) weeks. The median dose of emicizumab at the initiation of the maintenance phase was 5.9 (IQR 5.5–6.2) mg/kg/4 weeks with dosing intervals ranging between 7 and 28 days, as demonstrated in Figure 2. While most adult/adolescent PwHA (n = 74) were treated with the registered dosing intervals of 7 or 14 days with entire-vial dosing, most children (n = 17) had alternative dosing intervals, usually 21 days (n = 12, 38%). Six adolescents self-reported non-adherence to emicizumab treatment; their median age was 17 (IQR 15–20 and range 13–24) years. Their emicizumab consumption was only 53% (range 31−81%) of the prescribed amount.