Twenty years' observation of subcutaneous pollen allergoid immunotherapy efficacy in adults.

Introduction: It is valuable to determine the long-term efficacy of allergen-specific immunotherapy (SIT) and whether it can cure allergy.

Aim: For this study, patients were prospectively observed for 20 years after completion of SIT to determine its effectiveness.

Material and methods: A total of 1006 patients who underwent SIT for pollen allergy were observed for 20 years to assess the efficacy of SIT. The rhinitis symptom score (RSS) and asthma symptom score (ASS) were measured after SIT completion. The possibility of allergy cure was estimated based on three sets of criteria: group A - neither symptoms nor intake of medication during the analysis period, group B - no symptoms during the analysis period (but possible medication intake), and group C - at most one mild symptom during the analysis period.

Results: After SIT, approximately 25% of patients showed complete relief of allergy symptoms and had no need for symptomatic drug treatment during the pollen season. The level of effectiveness of SIT was similar throughout the treatment period. During the observation period after SIT, RSS ranged from 1.51 to 1.82, and ASS ranged from 1.22 to 1.29. The treatment effect at 10 and 20 years after SIT was comparable, regardless of whether criterion A or B was used. However, the effect of SIT using criterion C was lower than those using criteria A and B for the analyzed time points.

Conclusions: For this study cohort, SIT had a long-term effect that did not depend significantly on the duration of immunotherapy against pollen.