Clinical Outcomes in Placebo-Injection and Injection-Free Cohorts in Birch Pollen Allergy: An Exploratory Cross-Study Comparison

Background/Objectives: Placebo responses can complicate the interpretation of allergen immunotherapy (AIT) trials because symptom- and medication-based outcomes may be influenced by the trial context in addition to treatment-specific effects. Injection-free comparison cohorts are rarely available in conventional double-blind, placebo-controlled AIT trials. We therefore conducted an exploratory post hoc cross-study comparison of clinical outcomes in two placebo-injection cohorts and an injection-free cohort of birch pollen-allergic participants.

Methods

Data from three prospective clinical studies evaluating the mannan-conjugated birch pollen allergoid EP-088-T502—T502-SIT-020, T502-SIT-045, and T502-SIT-068—were assembled for this cross-study comparison. Placebo-injection cohorts from studies T502-SIT-020 and T502-SIT-045 were compared with the injection-free cohort from study T502-SIT-068. Clinical outcomes included the Combined Symptom and Medication Score (CSMS), daily Symptom Score (dSS), and daily Medication Score (dMS).