Long-term impact of a birch/alder/hazel or birch-only liquid sublingual immunotherapy on birch-family pollen respiratory allergy: A real-world study

Background: Patients with allergic rhinitis (AR) and/or mild or moderate asthma derived from birch-family pollen allergy can be treated with liquid sublingual immunotherapy (SLIT-liquid). This study evaluated the impact of two SLIT extracts on AR and asthma progression or onset in these patients. Methods: This was a sub-analysis of a retrospective, longitudinal comparative cohort study that used a German prescription database. Patients treated with 3-tree (birch/alder/hazel) or birch-only SLIT-liquid and followed up for up to 6 years after treatment were compared with controls dispensed symptomatic medications. Multiple regression analysis compared dispensation data as a proxy for disease status and progression. Results: A total of 493 patients treated with 3-tree SLIT-liquid and 311 treated with birch SLIT-liquid were analysed vs. 44,835 patients included as controls. Overall, 70.5 % of patients presented solely AR, 24.2 % solely asthma, and 5.3 % both diseases. Compared with controls, patients treated with 3-tree SLIT-liquid had reduced risk of AR [odds ratio (OR) = 3.21, 95 % CI 2.54–4.06, p < 0.001], asthma progression (OR = 2.03, 95 % CI 1.43–2.89, p < 0.0001), or asthma onset (OR = 0.592, 95 % CI, 0.408–0.860, p = 0.006). Birch-only SLIT-liquid showed similar effectiveness in reducing AR and asthma medication dispensation but no significant effect in reducing new-onset asthma. Conclusions: This real-world study demonstrated the effectiveness of treatment with 3-tree SLIT-liquid or birch SLIT-liquid in slowing the progression of birch-family pollen allergy. 3-tree SLIT-liquid covering a broader repertoire of epitopes mimicking natural exposure throughout the year may be valuable for patients sensitised to birch and/or alder and/or hazel pollen suffering from overlapping tree-pollen seasons.