Dear Dr. K: Please give us an update on the vaccine for peanut allergy.
Your request is very timely as I recently finished reading a pro/con editorial in the journal Asthma and Allergy Proceedings. I think these two editorial viewpoints sum things up quite nicely. The first of the two is titled, “Oral and Sublingual Peanut Immunotherapy Is Not Ready for General Use.” In this article written by the director of allergy at the University of Michigan, the focus in on the high frequency of patients who experience symptoms from the oral vaccine – including anaphylaxis – which required use of epinephrine.
Analyzing five recently published trials on peanut vaccine revealed that in each study, more than one half of patients had some type of reaction as the vaccine was built up. The reactions led to some parents removing their children from the study. In the five protocols reviewed the drop-out rate varied from 5 to 25 percent.
The author points out that the vaccine works by two mechanisms: tolerance and desensitization. Tolerance occurs by depleting the allergic antibody (IgE) to peanut. To maintain the depletion, the vaccine must be continued daily. If the vaccine is stopped, tolerance also stops because IgE rebuilds itself.
Desensitization is what occurs with traditional allergy shots. It leads to an increase in protective IgG against peanut (called blocking antibody), and a decrease in IgE. This type of protection is more desirable and can persist even after the vaccine is stopped. The author points out that even though the vaccines do seem to elicit both modes of protection, no long-term study has been done to show how long-lasting the benefit is. Therefore, the author concludes that for now, the vaccine should be restricted to research protocols until the risk/benefit ratio is better understood and the long-term benefit is fully determined. The contrasting editorial is from the Paul Foster School of Medicine in El Paso, Texas, and is titled, “Oral Immunotherapy for Peanut Allergy in a Clinical Practice is Ready.” This author argues that the annual rate for accidental peanut ingestion is 10 percent which leads to severe symptoms, including anaphylaxis and the need for epinephrine. This number far exceeds the number of vaccine-induced reactions requiring epinephrine. He further argues that peanut allergy has a major effect on the quality of life of the patient and his/her family, and can be psychosocially debilitating. Also, unlike other food allergies where remission is high, less than 20 percent of peanut allergic children have spontaneous remission. Finally, he cites the outcome of three clinical trials done in office-based settings that treated a total of 150 children. Of these, 111 were successfully able to take the vaccine and were protected in a purposeful challenge of eight peanuts.