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

Safety of SCIT

Systematic reviews have shown that SCIT is a safe therapeutic intervention when it is prescribed to well-selected patients, and given in a specialist clinic with adequate facilities and by trained medical personnel.

SCIT is associated with a risk of systemic side effects and anaphylaxis. SCIT can produce both local and systemic adverse reactions; however, in the majority of cases these symptoms are readily reversible if recognized early and with prompt treatment. The risk is greater in subjects with asthma[25,26] and with accelerated dosing schedules.

Adverse effects may occur with all allergen preparations whether using standardized extracts, allergoids or recombinant allergens.[13]

The safety of SCIT was evaluated in a Cochrane systematic review of 51 RCTs for seasonal AR.[18] Following the European Academy of Allergy and Clinical Immunology Systemic Reactions Grading System,[27] the authors found that:

  • A total of 22% of SCIT versus 8% of placebo recipients had mild (grade 2) reactions;

  • A total of 7% of SCIT versus 1% of placebo recipients had moderate-to-severe (grade 3) reactions;

  • Anaphylaxis (grade 4) was reported in only three cases in the SCIT group (0.72%) versus one case in the placebo group (0.33%);

  • Adrenaline was used in 3.4% of participants (19/557 patients; 0.13% of 14,085 injections) in the SCIT group versus 0.25% (1/404 patients; 0.01% of 8278 injections) in the placebo group;

  • This review suggests that adverse reactions serious enough to require treatment with adrenaline (epinephrine) occur approximately once in every 770 immunotherapy injections;

  • There were no fatalities associated with SCIT for seasonal AR.

Pretreatment with oral H1-antihistamines during the induction and maintenance phases seems to reduce the frequency and severity of systemic side effects.[28]

Recently, a universal terminology and grading system for SCIT-related adverse events has been published and should be implemented when reporting adverse reactions due to SCIT.[29]

In a 3 year collaborative American Academy of Allergy, Asthma & Immunology/American College of Allergy, Asthma & Immunology Immunotherapy Safety Surveillance study, there were no fatalities reported in the approximately 8.1 million injections administered by 1922 SCIT prescribers in the period from June 2008 until July 2009.[30] A total of 82% of 806 practices reported a total of 8502 SCIT SRs (SR rate: 10.2 SRs per 10,000 [0.1%] injection visits).[30] Most of these SRs were categorized as grade 1 (74%) or grade 2 (23%) SRs and occurred within 30 min. However, 3% of the reported SRs were grade 3, which was defined as "severe, life-threatening anaphylaxis: severe airway compromise due to severe bronchospasmor upper airway obstruction with stridor or hypotension." This would translate into three severe SRs per 100,000 injection visits. A total of 14% of the SRs were delayed in onset (>30 min after the injection).[31] Most delayed-onset SRs were grade 1 but 3% were grade 3 reactions.

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