Double-blind, placebo-controlled study with a modified therapeutic vaccine of Salsola kali (Russian thistle) administered through use of a cluster schedule

BackgroundThe inhalation of Salsola kali pollen is a common cause of respiratory diseases in Europe and North America.ObjectiveTo evaluate the efficacy and safety of a depigmented and glutaraldehyde-polymerized therapeutic vaccine of S kali.MethodsThe trial was randomized, double-blind, and placebo-controlled using a rush protocol in the build-up phase. Sixty patients with rhinoconjunctivitis (19 also had mild asthma) were randomly allocated to receive either active treatment (polymerized extract) or placebo. The final distribution was 41 patients in the active and 19 in the placebo group. Side effects were registered. Symptom and medication scores and the number of days free of symptoms during the pollen season were assessed to evaluate the clinical efficacy. A Rhinoconjunctivitis Quality of Life Questionnaire was completed in the previous pollen season (before treatment) and during the pollen season 1 year later (in the trial). Dose-response skin tests were performed at baseline and at the end of the trial.ResultsThere was a significant difference (P < .05) in symptom and medication scores between both groups during the pollen season, with the active group the one that had fewer symptoms and lower intake of medication. The number of days without symptoms was higher in the active group (P < .05). This group also had a significant improvement in the Rhinoconjunctivitis Quality of Life Questionnaire and a reduction in skin sensitivity. No moderate or severe systemic reactions were registered.ConclusionImmunotherapy with this modified vaccine of S kali pollen is safe and efficacious to treat patients clinically sensitive to this pollen.Clinical implicationsPatients allergic to S kali (Russian thistle) can be successfully treated with immunotherapy to improve symptoms of allergic rhinitis and asthma, reduce medication use, and improve quality of life parameters.