Impact of Dose Adjustment After Gaps in Subcutaneous Immunotherapy: Update From the North American Immunotherapy Surveillance Study (2008-2023).

Abstract

Protocols for adjusting allergy injection doses after gaps in therapy, and optimal intervals for maintenance injections, are based on expert opinion only. To assess (1) incidences of systemic allergic reactions (SRs) to subcutaneous allergen immunotherapy (SCIT), (2) clinical practices that reduce the risk of SRs, (3) SCIT-related infections, and (4) risks associated with interruptions in SCIT. From 2008 to 2023, members of the American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma, & Immunology completed annual surveys of SCIT-related SRs; SCIT-related infections were assessed since 2014. Questions were added in 2020 regarding dose adjustment after gaps in immunotherapy, and maintenance intervals prescribed. Data were gathered on 84.1 million injection visits and 4.9 million patients (2008-2023). Four new SCIT-related fatalities were confirmed (2018-2023). One contaminated vial, resulting in 2 local skin infections, was identified (2014-2023). Practices reducing to 1 vial lower in patients who were more than 7 weeks late for maintenance vial injections had fewer grade 4 SRs (P = .02). Practices decreasing to the next lower vial in patients who were more than 28 days late during buildup had fewer grade 3 and 4 SRs (P = .03). For the period from 2021 to 2022, there was an increased rate of total (P < .0001), grade 2 (P < .0001), and grade 3 SRs (P = .0005) for practices that used a maintenance injection interval longer than 4 weeks. Fatal reactions to SCIT still rarely occur. The risk of infections from SCIT is extremely low. Controlled studies are needed to define optimal dose adjustment strategies after gaps in therapy as well as the safest, most efficacious maintenance intervals for aeroallergen SCIT.