Safety of immunotherapy with therapeutic vaccines containing depigmented and polymerized allergen extracts

The major complication of allergen immunotherapy is a severe reaction. To evaluate the safety of depigmented and glutaraldehyde-modified allergen extracts in a large group of patients undergoing immunotherapy treatment. Seven hundred sixty-six patients, having rhinoconjunctivitis and/or asthma, were entered in a prospective, multi-centre, observational cohort study, to evaluate the safety of immunotherapy with modified allergen vaccines. Patients were sensitized to mites and/or pollen and received a therapeutic vaccine containing depigmented and polymerized allergen extracts of mites and/or pollens adsorbed onto aluminium hydroxide. The schedule of administration consisted of a build-up phase of 4- to 6-weekly injections, followed by 12-monthly injections of the maintenance dose. Tolerance was assessed by recording all side reactions related to immunotherapy. All patients completed the study. Fifty-four clinically relevant local reactions (43 immediate and 11 delayed) were observed (0.4% of injections). The systemic reactions were 34 in 12 patients. Six reactions were immediate (all of grade 2) and 28 delayed (18 of grade 1 in two patients, nine of grade 2 and one of grade 3). The systemic reactions of grade 2 or 3 occurred in 0.12% of the injections. All systemic reactions were mild and resolved spontaneously without the need for medication. Specific immunotherapy using modified allergen vaccines is safe to treat allergic patients. The percentage of adverse reactions detected is lower than those reported in the literature with native-unmodified allergen extracts.