目的 探讨1岁以下重型血友病A（hemophilia A, HA）患儿接受减低剂量艾美赛珠单抗（emicizumab, EMI）治疗的有效性和安全性。 方法 回顾性收集2022年7月—2025年6月于深圳市儿童医院血液肿瘤科接受减低剂量EMI治疗的11例年龄≤12个月的重型HA患儿资料，对其治疗的有效性及安全性进行统计分析。 结果 11例患儿开始使用EMI的中位年龄（范围）为7.9（4.2~11.2）个月，EMI的中位负荷剂量（最初4周的剂量）（范围）和中位维持剂量（范围）分别为6.2（2.8~12.6）mg/（kg·4周）和3.1（2.0~4.8）mg/（kg·4周）。EMI预防治疗的中位时长（范围）为15.8（1.7~36.0）个月。治疗后出血指标：年化出血率、自发性年化出血率及年化治疗出血率的中位数（范围）分别为0.5（0~6.2）、0（0~0.5）和0（0~3.0），均较治疗前降低，其中自发性年化出血率在治疗前后的差异具有统计学意义（P<0.05）。64%（7/11）的患儿未发生需治疗的出血事件，所有患儿均无EMI相关不良事件。 结论 减低剂量EMI用于婴儿血友病A患者预防治疗可以有效控制出血，治疗效果显著，安全性好。

Objective To investigate the efficacy and safety of reduced-dose emicizumab (EMI) prophylaxis in infants under one year of age with severe hemophilia A (HA). Methods Medical records of 11 infants aged ≤12 months with severe HA who received reduced-dose EMI in the Department of Hematology and Oncology, Shenzhen Children's Hospital, from July 2022 to June 2025 were retrospectively reviewed. Efficacy and safety were analyzed statistically. Results The median age at EMI initiation was 7.9 months (range 4.2-11.2 months). The median loading dose (first 4 weeks) and median maintenance dose were 6.2 mg/kg per 4 weeks (range 2.8-12.6 mg/kg per 4 weeks) and 3.1 mg/kg per 4 weeks (range 2.0-4.8 mg/kg per 4 weeks), respectively. The median duration of EMI prophylaxis was 15.8 months (range 1.7-36.0 months). After treatment, the median (range) annualized bleeding rate, spontaneous annualized bleeding rate, and annualized treated bleeding rate were 0.5 (0-6.2), 0 (0-0.5), and 0 (0-3.0), respectively. All decreased compared with pre-treatment, and the reduction in spontaneous annualized bleeding rate was statistically significant (P<0.05). Overall, 64% (7/11) of patients experienced no bleeding events requiring treatment. No EMI-related adverse events were observed. Conclusions Reduced-dose EMI prophylaxis effectively controls bleeding in infants with hemophilia A and shows good safety.