Allergen Immunotherapy and 36-Month Allergic Respiratory Disease Trajectories: A Target-Trial

Allergen immunotherapy (AIT) may modify allergic respiratory disease, but its association with progression and remission in routine practice remains uncertain.

We emulated a target trial in a single-center retrospective cohort at AlergiaMx, Mexico City, using data from 2020 to 2025. We compared sublingual allergen immunotherapy initiation within a 14-day grace period with non-initiation among AIT-eligible patients. Follow-up extended up to 36 months, and propensity-score overlap weighting addressed baseline confounding.

Among 2,713 patients, 1,971 initiated AIT and 742 did not. Weighted disease worsening was 46.3% versus 63.6% (relative risk [RR] 0.73, 95% confidence interval [CI] 0.65-0.82), and sustained progression was 8.4% versus 17.0% (RR 0.49, 95% CI 0.35-0.69). At 36 months, clinical remission was 47.0% versus 18.3% (RR 2.57, 95% CI 1.93-3.43), and treatment-associated remission was 31.7% versus 5.8% (RR 5.44, 95% CI 3.23-9.16). Longitudinal differences favored AIT for asthma control, quality of life, and fractional exhaled nitric oxide.

AIT initiation was associated with less worsening, greater remission, and favorable clinical and inflammatory trajectories over 36 months. These observational findings do not establish a causal disease-modifying effect; residual confounding and differential follow-up remain possible.