Fire ant Immunotherapy with inteRvals Extended to 12 weekS: The FIRES study

Background: There are no studies describing 12-week extended maintenance interval (EMI) immunotherapy (IT) efficacy in preventing anaphylaxis to imported fire ant (IFA) stings. Objective: The purpose of this study was to determine the safety and efficacy of 12-week maintenance intervals in patients treated with IFA IT. Methods: After a minimum of 3 months of conventional maintenance interval IT and verification of baseline efficacy, adults with IFA hypersensitivity were prospectively enrolled and extended their maintenance doses to 6-, 8-, and 12-week intervals. Efficacy was confirmed by means of an annual IFA sting challenge. Results: A total of 25 patients initiated EMI. The severity of their initial systemic reactions was mild in 8 patients (32%), moderate in 10 patients (40%), and severe in 7 patients (28%). Maintenance IT duration at trial entry was less than 3 years in 18 patients (mean 11 months; range 3-28 months), 3 to 5 years in 4 patients (mean 46 months; range 36-57 months), and greater than 5 years in 5 patients (mean 111 months; range 67-197 months). The treatment cohort did not experience systemic reactions to extended interval injections, cluster refill injections, field stings, or sting challenges. Conclusion: This prospective longitudinal cohort study revealed that in adults 18 years old or older who have received at least 3 months of maintenance dose IFA–whole body extract IT with proven efficacy, extension to a 12-week EMI is a safe effective treatment option. The benefits of EMI include a reduced number of injections, clinic visits, and lapses in maintenance IT.