Is faster safer? Cluster versus short conventional subcutaneous allergen immunotherapy

Aim: Few studies have compared cluster immunotherapy and conventional administration regimens. The aim of this study was to establish the safety profile of these different regimens in patients with allergic respiratory diseases who received index-of-reactivity (IR)-standardized allergen extracts by the subcutaneous route. Materials & methods: The safety of subcutaneous immunotherapy (SCIT), administered by means of a 4-week cluster titration schedule (cluster-SCIT) or by an 8-week short conventional titration schedule (SC-SCIT), both with a target dose of 8 IR, was assessed in a retrospective, observational, multicenter study. Results: A total of 658 patients (339 cluster-SCIT and 319 SC-SCIT) were recruited from 92 sites in Spain. Injection site reactions occurred in 25.1 and 27.3% of patients treated with cluster-SCIT and SC-SCIT, respectively. Systemic reactions (European Academy of Allergy and Clinical Immunology criteria) were reported for 0.2% of doses and 1.5% of patients with cluster-SCIT, and 0.7% of doses and 4.4% of patients with SC-SCIT. Most reactions were mild and there were no grade 3 or 4 systemic reactions. No life-threatening systemic reactions, anaphylactic shock, or adverse events leading to therapy discontinuation were reported. Conclusion: The safety profile of the cluster regimen supports the use of accelerated SCIT schedules with IR-standardized allergen extracts compared with short conventional schedules, particularly if similar extracts and application methods are used.