Treatment of allergic rhinitis with allergen immunotherapy in children and adolescents—Adherence, rhinitis severity, and asthma onset

BACKGROUND: Sublingual immunotherapy (SLIT) has been used to reduce symptoms in allergic rhinitis and to prevent asthma onset. Many studies lack level of adherence and standardized endpoints based on international guidelines. OBJECTIVE: We aimed to study the long-term outcomes of allergic rhinitis severity and asthma onset by adherence of SLIT to grass and birch allergens in children and adolescents with allergic rhinitis. METHODS: In a population-based register study, we included all children 5-17 years, with initiation of SLIT between 1 July 2006 and 30 June 2022. Allergic rhinitis severity and asthma onset were based on diagnosis and treatment. Adherence was measured for one, two, and 3 years and divided into low, moderate, and high and compared to only one prescription (reference). RESULTS: 7222 children were treated with grass pollen extract and 1184 with birch pollen extract. A significantly lower allergic rhinitis severity was seen in adjusted analyses with odds ratios (OR) of 0.85 (95% confidence interval: 0.72-0.99) and OR 0.81 (0.67-0.96) for the high adherence group (i.e., only one prescription) compared to the reference group in the second and third year respectively after SLIT grass initiation. No statistically significant difference was seen for asthma onset. Estimates for birch SLIT were less conclusive. CONCLUSION: We found reduced allergic rhinitis severity with higher adherence and longer treatment duration, particularly for grass SLIT. Shorter follow-up for birch SLIT and smaller sample size for asthma onset probably influenced our results. The results should encourage clinicians to prescribe SLIT for eligible children and motivate patients to 3-years full adherence.