Persistence of efficacy after a brief course of polymerized ragweed allergen: A controlled study☆

Abstract Immunotherapy with PRW has been demonstrated to be safe and effective. To determine whether the efficacy would remain in successive ragweed seasons without further therapy, a trial was conducted comparing PRW to histamine placebo therapy in patients that had received courses of PRW previously. Those patients were also compared to previously untreated ragweed-sensitive patients. In a double-blind fashion, 21 previously treated patients were treated before the 1982 ragweed season with four weekly injections of PRW therapy, whereas 21 previously treated patients were treated with four injections of placebo therapy. An additional control group of 21 previously untreated ragweed-sensitive patients received no injections. Daily symptom and medication score sheets were completed by patients each day of the ragweed season. Blocking antibody rose elevenfold with treatment ( p p p