A double-blind, placebo-controlled trial of polymerized whole ragweed for immunotherapy of ragweed allergy

Immunotherapy with polymerized ragweed (PRW) has been demonstrated to be safe and effective when compared with monomeric ragweed or untreated controls. To further establish the efficacy of PRW, a trial was conducted comparing PRW, placebo, and no treatment in ragweed-sensitive individuals. In a double-blind manner, 21 patients were treated before the 1981 ragweed season with 15 weekly injections of PRW totaling about 50,000 PNU and 1200 microgram antigen E, while 19 patients were treated with 15 weekly injections of a caramelized glucose and histamine placebo. An additional control group received no injections. Blood was drawn for IgE against ragweed antigen E (IgE-a-AgE) and for blocking antibody against AgE before treatment, after treatment (before season), and after season. In the untreated patients, blood was drawn before season and after season. Daily symptom score sheets were completed by patients each day of the ragweed season. Blocking antibody rose more than 40-fold with treatment (p = 0.0001) in the PRW group but was unchanged in the placebo group with treatment. IgE-a-AgE rose with PRW therapy. Clinical efficacy of PRW was again confirmed in this study. Symptom score mean in the PRW group was statistically lower than the mean in the placebo group (p = 0.022) and in the untreated group (p = 0.018). There were no systemic reactions and only minor local reactions during treatment. In summary, PRW is an improved form of immunotherapy.