Background Subcutaneous immunotherapy is effective for the treatment of respiratory allergy, and it is largely used in Italy, but no systematic safety assessment has been carried out so far.
Objective To assess prospectively the safety of injection immunotherapy in a multicentre, real-life survey.
Methods Eleven Italian allergy departments recorded the clinical characteristics of systemic reactions (SRs) due to immunotherapy. Vaccines were prescribed according to guidelines; only standardized depot extracts were used. SRs were graded according to the EAACI recommendations, and were classified as immediate or delayed.
Results One thousand seven hundred and thirty-eight patients (847 males, age range 5–71) received immunotherapy from eight different manufacturers, for a total of 2038 courses (300 patients received two extracts). A total of 60 785 injections were given over a mean immunotherapy duration of 3 years. Overall, 95 reactions were observed in 57 patients (3.28%), corresponding to 4.7% of the courses and 1.56/1000 injections. Twenty-five patients experienced more than one adverse event. There were 34 grade 2, 60 grade 3 and one grade 4 reactions and no fatality. SRs occurred more frequently in patients with asthma than in patients with rhinitis alone (4.1% vs. 1.1%), and were equally distributed between the build-up and the maintenance phase. Ragweed and grass extracts caused significantly more side effects than other allergens.
Conclusion In this large prospective study, the rate of SRs was low, thus confirming that injection immunotherapy has an acceptable risk/benefit ratio when prescribed and carried out according to recommendations.