Long-Term, Real-World Effectiveness of Allergen Immunotherapy in Children and Adolescents With Allergic Rhinitis and Asthma

Background: Respiratory allergies often begin in childhood and can progress over time, leading to increased disease burden. Allergen immunotherapy (AIT) is the only causal treatment for allergic respiratory diseases with disease-modifying potential. While randomised trials support its efficacy in controlling allergic rhinitis (AR) and asthma symptoms, long-term real-world data in children remain limited. Methods: This paediatric study (n = 11,036) was conducted within the pre-defined framework of the REACT study, based on protocol-specified objectives. Children (< 18 years) with physician-diagnosed AR, with or without pre-existing asthma, were included. AIT-treated patients were matched 1:1 to non-AIT controls. Effectiveness was assessed over 9 years by comparing AR and asthma medication prescriptions, using a public database covering all reimbursable AIT products. Relative differences were calculated across the full observation period. Results: AIT-treated children (mean age 11.4 years; 62.1% male) exhibited greater reductions in AR medication use than controls (additional 9% reduction beyond 61% in controls). In children with asthma, AIT was associated with additional reductions in asthma medication use (-21% beyond -48% in controls), severe exacerbations (-21% beyond -36%), and new oral corticosteroid prescriptions (-33% beyond -41%). Age stratification revealed more pronounced AR medication reductions in younger children (0-11 years) than in adolescents (12-17 years). Conclusion: This large-scale, real-world study supports the long-term effectiveness of AIT in children with AR, with or without asthma. The findings reflect improved disease control and suggest a disease-modifying effect of AIT. Early intervention, particularly in younger children, may help mitigate the progression of allergic disease.