Discontinuation of Ragweed Immunotherapy
The optimum duration of ragweed immunotherapy is unknown. Trials of venom immunotherapy for persons sensitive to bee sting indicate that discontinuation after three years is generally safe and effective. To discern whether discontinuation of ragweed immunotherapy after at least three years’ participation was as efficacious as continuation of the therapy longer, a group of 20 patients was evaluated.
At the beginning of the trial, subjects (each of whom had been receiving at least three years of immunotherapy with ragweed antigen) were challenged with ragweed antigen instilled nasally. The number of sneezes induced and amount of inflammatory mediator response within the nose were then measured. Over the ensuing year, one group continued on immunotherapy, and the other received placebo injections. During the intervention year, an allergy symptom diary was kept in both groups.
One year later, the recipients of active immunotherapy showed no change in symptoms, sneezes, or inflammatory mediator release in response to challenge. The placebo recipients demonstrated no significant change in overall symptom scores. On the other hand, more subtle markers of disease activity, such as inflammatory mediator levels in response to challenge, protective IgG antibody levels to ragweed, and number of sneezes post-challenge, did deteriorate among the placebo recipients. Markers of ragweed allergy disease activity are adversely affected by discontinuation of immunotherapy at the three-year point. Whether this will translate into actual loss of symptom control or long-term disease deterioration remains unknown.
Naclerio RM, et al. J Allergy Clin Immunol 1997;100:293-300.
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