Evaluation of the protocol for rush subcutaneous immunotherapy with birch pollen extract

We previously reported the effectiveness of rush subcutaneous immunotherapy with birch pollen extract (Birch rSCIT) for pollen-food allergy syndrome (PFAS) and the high rate of systemic reactions (SR) during the rapid escalation phase. In this study, we examined whether modifying the dose escalation protocol of Birch rSCIT would reduce SR and maintain therapeutic effects. Birch rSCIT was introduced in 20 patients with PFAS who experienced systemic symptoms upon ingestion of soybeans. Birch rSCIT was implemented using 3 protocols: 2 protocols (nonstep-up group) increased the target dose to more than 1:2 × 10² (w/v) in 0.05 mL, while 1 protocol (step-up group) increased the target dose to 1:2 × 10³ (w/v) in 0.3 mL, and then increased to 1:2 × 10² (w/v) in 0.05 mL using the conventional method in the following week. In the nonstep-up group, 4 out of 5 patients (80%), and in the step-up group, 2 out of 15 patients (13.3%) developed SR during rapid escalation. During the rapid escalation phase, the step-up group had significantly fewer SR than the nonstep-up group (P = 0.014). The median ingestible dose of soy milk in the oral food challenge was 3.5 mL before the treatment and increased significantly to 200 mL 1 year after initiating Birch SCIT (P < 0.01). We confirmed that reducing the target antigen dose in Birch rSCIT improved safety and maintained the therapeutic effect for soybean allergy with PFAS.