Safety of an Accelerated Build-up Phase With Pollen Allergoids: A Retrospective Study

Background: The introduction of chemically modified allergens (high-dose hypoallergenic preparations, or allergoids) has made it possible to safely accelerate the build-up phase, and pollen allergoids have proved effective and safe with only 7 pre-seasonal injections. The aim of this retrospective study was to investigate the safety of the abbreviated build-up phase of pollen allergoids in real life. Methods: We sent a questionnaire to allergy centers that adopted the shortened build-up schedule. The questionnaire included the following items: age, gender, symptoms, extract composition, maximum dose reached (yes/no), number of injections, local reactions (>5 cm, <10 cm), large local reactions (>10 cm), and systemic reactions. The shortened regimen was administered with Allergovit (Allergopharma GmbH & Co. KG), an AIT pollen extract that has been chemically modified with formaldehyde to produce an allergoid. The abbreviated up-dosing regimen consists of 4 injections, and the schedule is completed within 3 weeks only. Results: All patients but one reached the maximum scheduled dose, and 138 patients (88.5%) completed the treatment without reactions. A further 138 patients (88.5%) also reached the maximum dose with the 4 scheduled injections. Eighteen patients required 1 extra injection, 9 for concomitant non– treatment-related events and 9 for adverse reactions. Overall, 12 mild treatment-related local reactions (>5 cm, <10 cm) and 2 severe local reactions (>10 cm) were recorded (2.2% of the total 649 injections; 9.0% of patients). A severe local reaction was the reason why 1 patient did not reach the maximum dose. No systemic reactions were observed. Conclusions: This study shows that the build-up phase of a high-dose hypoallergenic pollen allergoid can be safely shortened from the conventional 7 to only 4 injections, thus enabling the maintenance dose to be reached in only 3 weeks. Patients can benefit earlier from the treatment, since the clinical benefits of AIT appear very shortly after the maintenance dose is reached. Shortening the escalation period can also address the problem of poor adherence, since adherence to SCIT is affected by logistic difficulties in attending the health care facility to receive the medication.