Safety of 1 mcg/mL as the starting dose in cluster protocol for hymenoptera immunotherapy

Hymenoptera venom allergy is a potentially severe allergic reaction in the general population. The only preventative approach in these cases is venom immunotherapy (VIT), which follows different protocols. The recommended initial dose is 0.001-0.1 mcg of venom extract. However, few reports have declared the safety of 1 mcg venom as the starting dose.

The study was conducted on Iranian patients with a history of anaphylaxis to venom. Skin tests confirmed hypersensitivity to honeybee, yellow jacket, and/or paper wasp from subfamily Polistes using Apis melifera, Vespula spp, and Polistes spp venom extracts, respectively. Subsequently, the patients were treated with the cluster protocol.

Twenty-two patients (17 males and 5 females, aged 28.3±11.8 years) were enrolled in the study. Skin prick tests and intradermal tests showed positive results for yellow jacket in 17 (77.3%) and 21 (95.4%) patients, honeybee in 14 (63.6%) and 17 (77.3%) patients, and wasp in 14 (63.6%) and 17 (77.3%) patients, respectively. Upon administering the initial dose of 1 mcg/mL, 40.9% (9 cases) of patients presented mild local reactions, including 7 with yellow jacket allergy, 5 with honeybee allergy, and 3 with wasp allergy. One patient with yellow jacket allergy had a mild systemic reaction. Patients with a positive skin test for wasp had significantly lower rate of reactions after the first dose of venom (p=0.026). Throughout the entire build-up phase, more than 90% (20 of 22) of patients experienced mild local reactions, followed by large local reactions (3 cases, 13.6%), mild systemic reactions (1 case at 1 mcg/mL dose), and moderate-to-severe systemic reactions (3 cases, 13.6%). Large local and moderate-to-severe systemic reactions were detected after injecting 50 mcg (each one case) and 100 mcg (each 2 cases) of venom extracts.

This study recommends 1 mcg/mL of the venom extract as a safe starting dose for VIT. This accelerated protocol could successfully reduce the time and costs of therapy for patients undergoing out-patient cluster VIT.