To investigate the safety and efficacy of 2 extracts of echinacea for preventing upper respiratory tract infections.
Three-armed, randomized, double-blind, placebo-controlled trial.
Four military ...institutions and 1 industrial plant.
Three hundred two volunteers without acute illness at time of enrollment.
Ethanolic extract from Echinacea purpurea roots, Echinacea angustifolia roots, or placebo, given orally for 12 weeks.
Time until the first upper respiratory tract infection (time to event). Secondary outcome measures were the number of participants with at least 1 infection, global assessment, and adverse effects.
The time until occurrence of the first upper respiratory tract infection was 66 days (95% confidence interval CI, 61-72 days) in the E angustifolia group, 69 days (95% CI, 64-74 days) in the E purpurea group, and 65 days (95% CI, 59-70 days) in the placebo group (P = .49). In the placebo group, 36.7% had an infection. In the treatment groups, 32.0% in the E angustifolia group (relative risk compared with placebo, 0.87; 95% CI, 0.59-1.30) and 29.3% in the E purpurea group (relative risk compared with placebo, 0.80; 95% CI, 0.53-1.31) had an infection. Participants in the treatment groups believed that they had more benefit from the medication than those in the placebo group (P = .04). Adverse effects were reported by 18 subjects in the E angustifolia group, 10 in the E purpurea group, and 11 in the placebo group.
In this study a prophylactic effect of the investigated echinacea extracts could not be shown. However, based on the results of this and 2 other studies, one could speculate that there might be an effect of echinacea products in the order of magnitude of 10% to 20% relative risk reduction. Future studies with much larger sample sizes would be needed to prove this effect.
The efficacy of the active specific immunotherapy and immune prophylaxis against the Brown Pearce carcinoma in rabbits was tested. The tumor cells taken as antigens were either untreated or treated ...with Mitomycin C combined or not with vibrio-cholerae-neuraminidase. The immune prophylaxis using tumor cells prepared this way proved to be very effective. In contrast, immunotherapy of rabbits with tumors was not effective, even when immunization was started directly after transplantation. Possible mechanisms were analyzed in-vitro and in-vivo assays. The cellular reactivity of sensitized spleen cells was positive, the humoral reaction was weaker. This kind of reaction could only be demonstrated with tumor cells pretreated with vibrio-cholerae-neuraminidase. The findings shall only be discussed with respect to the possible causes of ineffective immunotherapy.
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