Multisite evaluation of fire ant venom immunotherapy safety and efficacy

Imported fire ant (IFA) venom immunotherapy (VIT) is the only disease-modifying treatment reported to be effective at decreasing the risk of systemic reactions (SRs) to IFA stings.

Our aims were to determine the baseline rates of IFA sensitization in subjects, describe IFA VIT prescribing patterns across the military health system (MHS), and retrospectively evaluate the safety and efficacy of IFA VIT.

We prospectively compared IFA sensitization in participants with and without an SR to flying Hymenoptera venom. Separately, IFA VIT prescription records were extracted from a centralized repository, and rates were described across the MHS. Additionally, we retrospectively reviewed the clinical course of patients being treated with IFA VIT at 11 military treatment facilities.

The in vitro IFA sensitization rates in our prospective cohort ranged from 19.1% to 24.1%. Sensitization rates did not differ statistically between the subjects with or without an SR to flying Hymenoptera venom. We found that 60.9% of all MHS IFA VIT prescriptions (491 of 806) were from the 11 facilities in this study. We retrospectively identified 137 subjects actively undergoing IFA VIT. Among the subjects actively undergoing IFA VIT, 28 reported an SR to IFA venom and repeat stings by IFAs after reaching VIT maintenance, and 85.7% (24 of 28) of the subjects noted symptoms no worse than a large swelling reaction after a repeat IFA sting. Notably, only 2.9% of the subjects (4 of 137) had an SR due to VIT.

This study's results align with those of prior IFA sensitization reports. A substantial proportion of patients undergoing IFA VIT experienced protection against anaphylaxis with reexposure, with relatively few adverse events.