Is Coseasonal Initiation of Allergen Immunotherapy Safe?

Published Online: February 1, 2016

Allergen immunotherapy (AIT) for allergic rhinitis is generally initiated several weeks before the start of pollen season to be fully effective. However, many patients do not seek treatment until the season has started and allergy symptoms have begun. Based on surveys of physicians and other observational reports of subcutaneously administered AIT, there is a perception that initiating AIT during the pollen season (coseasonal initiation) may increase the risk of systemic, serious, or severe side effects.   
In The Journal of Allergy and Clinical Immunology: In Practice, Creticos and colleagues published the results of a systematic review that assessed the safety of coseasonal initiation with subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) to validate or invalidate the perception of an increased safety risk. Publication databases were searched for studies of any design related to coseasonal AIT initiation up to March 2015. Eligible studies were those reporting safety data regarding coseasonal initiation of SCIT or SLIT (drops or tablets) for a pollen allergen in adults and children. Congress abstracts were included (6 studies).  

In all, 19 studies were identified, comprised of 8 SCIT studies (947 patients) and 11 SLIT studies (2,668 patients). Safety reporting and definitions of safety outcomes varied, which made comparison between initiation regimens difficult. No epinephrine administrations were reported in any of the studies. The frequency of discontinuation was ≤6% with coseasonal SCIT initiation and was ≤10% with coseasonal SLIT initiation, which is similar to the historical discontinuation frequency when AIT is initiated outside of the pollen season. In SCIT studies, systemic allergic reactions were reported in 0% to 7% of patients initiating treatment before the peak season, 0% to 6% of patients initiating after peak season or outside the pollen season, and 0% to 7% of patients who received placebo. In SCIT studies, serious side effects related to coseasonal initiation occurred in 0% to 2% of patients; few severe side effects were reported. In SLIT studies, systemic allergic reactions were reported in 0% to 4% of patients who initiated treatment coseasonally, 0% of patients who initiated outside the pollen season, and 0% to 2% of patients who received placebo. Overall, only 2 serious side effects related to coseasonal SLIT initiation were reported. Severe side effects were reported in 0% to 8% of patients who initiated coseasonally, 0% to 12% of patients who initiated outside the pollen season, and 0% to 8% of patients who received placebo.

It appears that coseasonal initiation of SCIT or SLIT may be possible without increasing the risk of systemic, serious, or severe side effects. Therefore, coseasonal initiation may be an option for patients already experiencing pollen-related allergy symptoms who may not otherwise receive AIT and could thereby benefit from its long-term disease-modifying effects. However, safety comparisons between coseasonal and non-coseasonal initiation regimens were hampered by differences in safety reporting and more data are needed to make definitive conclusions.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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