A prospective Italian survey on the safety of subcutaneous immunotherapy for respiratory allergy.

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.