Safety of subcutaneous immunotherapy in patients with severe asthma.

Background: Severe asthma (SA) has been identified as a risk factor for severe systemic reactions (SR) to allergen subcutaneous immunotherapy (SCIT). However, the incidence and characterization of SRs in SA in comparison to less severe or no asthma is not known.

Objective: The objective of this study was to characterize the incidence of SRs in patients with SA receiving SCIT in comparison to patients with no asthma or less SA.

Methods: A retrospective cohort study was performed on patients receiving SCIT from a multicenter national network of private allergy practices between January 2015 and December 2019. Demographics, asthma severity (International Classification of Diseases-10 codes), concomitant medications, aeroallergen skin testing, measures of asthma control with the asthma control test and forced expiratory volume in 1 second values, SCIT prescription, and an SR standardized form were assessed.

Results: A total of 65,855 patients, with 1072 patients having SA receiving SCIT, were included with a total of 4415 SRs (19.9 SR per 10,000 injection visits). Severe asthma had 23.9 SRs per 10,000 injection visits (incidence rate, 0.239; 95% confidence interval [0.189-0.298]). There were 155 grade III or IV SRs; 5 (3.2%) occurred in the SA group. There was no difference in rates of grade III or IV SRs between SA and no asthma and in rates of total SRs between SA and less SA.

Conclusion: In a large cohort of patients with SA undergoing multiallergen SCIT drawn from a diverse outpatient allergy population, the diagnosis of SA was not associated with increased moderate-severe SRs compared with patients without asthma and any severity of asthma.