Subcutaneous Allergen Immunotherapy for Allergic Disease

Examining Efficacy, Safety and Cost-Effectiveness of Current and Novel Formulations

Linda Cox; Moisés Calderón; Oliver Pfaar

Disclosures

Immunotherapy. 2012;4(6):601-616. 

In This Article

Persistent Effect of SCIT

At present, there are no specific tests or clinical markers that can distinguish which patients will remain in long-term clinical remission after discontinuing effective SIT,[52] but there is a growing body of evidence supporting its persistent efficacy. In contrast to pharmacotherapy, which appears to provide benefits only during treatment,[53] the clinical benefits associated with SIT may persist long after treatment cessation.[54–57]

The duration of SCIT efficacy has been most extensively studied in venom hypersensitivity with long-term follow-up studies suggesting that a 5 year VIT treatment course may be sufficient for most allergic individuals.[58–60] Although relapse rates as high as 15% of patients in the 10 year period after discontinuing VIT have been reported,[59,60] these post-VIT SRs were generally much milder than the pretreatment reactions and rarely severe.

In a double-blind, placebo-controlled study of patients with severe grass pollen AR who received 3–4 years of SCIT, followed by 3 years of continued SCIT or placebo, there was no significant difference in medication and symptom scores between the group that continued and the group that discontinued SIT.[54] There was a tendency for immediate skin test sensitivity to allergen to return, but there was a sustained reduction in the allergen late-phase skin response and associated immunological responses.

A prospective, controlled, follow-up study of children with AR ± asthma treated with 3 years of preseasonal grass SCIT or pharmacotherapy alone evaluated symptoms, medication use and objective parameters 6 and 12 years after treatment discontinuation.[55,56] Compared with the pharmacotherapy-alone group, the SCIT-treated patients had significantly lower medication use and symptoms during grass pollen season at both time points. Similar to the previously discussed study, skin prick test reactivity returned to the majority of the control group at 12 years after treatment cessation. The percentage of new allergy sensitizations, however, continued to be significantly smaller in patients with previous SIT (58%) compared with the controls (100%; p < 0.05) and there was a tendency for a lower prevalence of seasonal asthma in the post-SIT group (p = 0.08).

A controlled prospective study followed 40 asthmatic patients, who received 12–96 months of dust mite SCIT, for signs of relapse after discontinuation of treatment.[61] Relapse was defined as signs of asthma and/or rhinitis or impaired pulmonary function tests. Within 3 years of discontinuing SCIT, 55% of the patients were considered to have relapsed. A significantly higher relapse rate was seen among those who received SCIT for less than 35 months compared with those who received treatment for longer than 36 months (relapse in 62% of the <35 month treatment group vs 48% of >36 month treatment group; p < 0.04).

A study designed to assess the duration of efficacy of a 3 year course of SCIT on cat- or dog-induced asthma found that, although there was a significant increase in allergen-induced bronchial sensitivity (i.e., an objective SCIT outcome), almost all patients felt that they had improved cat tolerance with natural exposure compared with prior to their SCIT treatment (i.e., a subjective SCIT outcome).[62]

In general, the few studies specifically designed to evaluate the duration of SCIT efficacy for aeroallergen sensitivity have demonstrated long term clinical efficacy despite the apparent return of immediate hypersensitivity. Recently, a large clinical trial involving 257 patients demonstrated that the clinical and immunological changes associated with SLIT persist at least 2 years after treatment discontinuation.[63]

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