Venom Immunotherapy

By Kevin O. Hwang, MD, MPH 
Reviewed by Miriam K. Anand, MD, FAAAAI, FACAAI, Clinical Associate Professor, Arizona College of Osteopathic Medicine, Midwestern University; President, Allergy Associates & Asthma, Tempe, Arizona

Take Note

• A systematic review confirms that venom immunotherapy (VIT) reduces the risk of severe allergic reactions to subsequent insect stings and also improves quality of life.
• VIT itself can cause adverse reactions.

Stings from insects in the orderHymenoptera, which includes wasps, bees, and ants, have the potential to trigger severe allergic reactions. It is estimated that 0.3% to 7.5% of the general population has suffered a systemic reaction to an insect sting, while 2.4% to 26.4% have had a large local reaction, with prevalence estimates varying according to geographic location.1 Even among patients with large local reactions (and children with mild cutaneous reactions), however, the risk of a systemic reaction is estimated at 5% to 10%.2 Apart from the detrimental effect on physical health, allergic reactions to insect stings also cause many people to feel restricted in their daily activities.3 The general approach to insect venom allergy includes education on reducing exposure to subsequent stings and prescription of an epinephrine auto-injector. Venom immunotherapy (VIT) is commonly provided for patients who have had a severe reaction to an insect sting. This article will discuss the current evidence on the efficacy and safety of VIT.

Boyle and colleagues conducted a systematic review of VIT for preventing allergic reactions to insect stings in people who previously had a serious allergic reaction, defined as a systemic reaction or large local reaction to an insect sting, along with a positive skin test and/or serum-specific IgE to insect venom.4The review included 6 randomized controlled trials and 1 quasi-randomized controlled trial. All trials used VIT with extracted insect venom rather than whole body extract. Six trials used subcutaneous VIT while 1 used sublingual VIT. Participants in the control groups received placebo, no treatment, or back-up treatment. The primary outcome was a systemic allergic reaction to an insect sting “in the field” or a sting given as a challenge during treatment.

Meta-analysis of the data showed that VIT was effective for preventing a systemic allergic reaction to an insect sting. Overall, 3 of 113 (2.7%) participants treated with VIT had a subsequent systemic allergic reaction to a sting, compared with 37 of 93 (39.8%) participants in the control groups (risk ratio [RR] 0.10, 95% confidence interval [CI] 0.03 to 0.28). VIT also prevented large local reactions to insect stings (RR 0.41, 95% CI 0.24 to 0.69). The study could not draw conclusions on fatal reactions to stings because they were too rare. Two studies also demonstrated that VIT improved quality of life, as measured by the Vespid Allergy Quality of Life Questionnaire. Specifically, VIT improved quality of life by reducing anxiety and limitations to activities caused by fear of insect stings.

There was a significant risk of systemic reactions to the VIT treatment itself. Data from 6 of the trials showed that 14 of 150 (9.3%) participants treated with VIT and 1 of 135 (0.7%) participants in the control groups had a systemic reaction to the injections (RR 8.16, 95% CI 1.53 to 43.46).

There are also logistic challenges in providing VIT in clinical practice. “The main thing that people have problems with is the duration of therapy, which can be anywhere from 3 to 5 years,” says Susan Pacheco, MD, Associate Professor of Pediatric Allergy and Immunology at The University of Texas Medical School at Houston. “Parents are usually very good about bringing their child in for follow-up treatments, because they have a child who almost died. But sometimes adult patients think they won’t get stung again, so they might not come back to complete the treatment.”

Patients can also have local skin reactions to the VIT injections, which are not only uncomfortable, but may require medical intervention and delay completion of therapy. “Many times you have to taper the therapy by decreasing the dose or increasing the interval after a local reaction to the injections,” says Dr. Pacheco.

In summary, in people who have had a severe allergic reaction to an insect sting, VIT with extracted insect venom significantly reduces the risk of systemic and large local reactions to subsequent insect stings. VIT also improves quality of life. Challenges to providing VIT include adverse reactions to the treatment itself as well as patient noncompliance.

Published: 07/10/2014

References:

1. Bilò MB, Bonifazi F. The natural history and epidemiology of insect venom allergy: clinical implications.Clin Exp Allergy. 2009;39:1467-1476.
2. Golden DB. Insect sting anaphylaxis. Immunol Allergy Clin North Am. 2007;27:261-272.
3. Oude Elberink JN, Dubois AE. Quality of life in insect venom allergic patients. Curr Opin Allergy Clin Immunol. 2003;3:287-293.
4. Boyle RJ, Elremeli M, Hockenhull J, et al. Venom immunotherapy for preventing allergic reactions to insect stings. Cochrane Database Syst Rev. 2012;10:CD008838.