Long-term Efficacy of Allergen Immunotherapy

What Do We Expect?

Franco Frati; Ilaria Dell'Albani; Cristoforo Incorvaia


Immunotherapy. 2013;5(2):131-133. 

In This Article

Discussion & Significance

The literature on the long-term efficacy of SIT for respiratory allergy is not abundant. Most studies are based on SIT duration of 3 years, which is the currently recommended length of treatment.[9] Instead, the period of observation after stopping SIT is quite variable, though most studies are based on time points within 3 years. Such time is surely sufficient to show the advantage of SIT over drug treatment concerning the cost–effectiveness. In fact, the persistence of the clinical efficacy after treatment discontinuation is exclusive of SIT and achieves a progressive economic benefit for healthcare systems.[10] However, a longer time interval may be needed to show very long-lasting clinical efficacy, as observed in patients allergic to Hymenoptera stings treated with VIT, in whom a course of 5 years is currently recommended based on the observation that such duration provides the persistence of tolerance to stings 15 years after stopping the treatment.[11] The actual issue concerns what we expect from SIT: a complete cure of allergy or a momentary remission followed by a possible new treatment when the symptoms will reoccur? This is obviously related to the natural history of the disease. In a 23-year follow-up study on 738 college students with seasonal allergy, it was observed that at the end of follow-up, 55% of subjects had noted improvements (23% being symptom-free), while 33% were unchanged and 9% had worsened.[12] Therefore, the natural history has various trends in different individuals and this unavoidably influences the long-term outcome of SIT. It is likely that a trend towards improvement is associated with a longer duration of SIT efficacy, while the opposite may occur in subjects with a trend towards worsening; however, there is currently no possibility of predicting the course of allergy in single patients.