In a study appearing in the Journal of Alternative and Complementary Medicine (2005; 11(6): 1021-6) found that Echinacea may be effective in preventing upper respiratory infections (URIs). Subjects of the study were 402 children who had taken part in an earlier study that was randomized, double-blind and placebo-controlled; it tested the efficacy of Echinacea in treating upper respiratory infections.

The data from the earlier study was used for this, more recent study to determine if taking the Echinacea protected from subsequent URIs. There was a slight reduction in URIs for the children who had taken Echinacea; 55.8% had a second URI, compared to 69.2% in the control group.