Despite improvements in preventive and therapeutic measures, acute respiratory infections ("colds") remain a significant problem for modern health care in all countries of the world. For colds, patients often do not go to the doctor and prefer to independently use the medications recommended for over-the-counter medications, including herbal remedies. Echinacea is one of the most popular drugs. Clinical studies of echinacea drugs are primarily focused on the treatment and prevention of upper respiratory tract infections. To date, more than 30 clinical trials have been conducted in which the efficacy of echinacea preparations for colds has been studied; in addition, several meta-analyzes were performed.

It should be noted that studies on the effectiveness of echinacea preparations for naturally occurring upper respiratory tract infections are heterogeneous in design. In addition, various interfering factors appear which affect the possibility of subsequent comparison of research results (for example, the time differences between the onset of symptoms of the disease and the treatment, the dose used and the duration of treatment). Studies carried out on volunteers experimentally infected with a viral infection make it possible to standardize the time before treatment, the type of virus causing the disease, the dose of the drug and the state of the immune system (or immunocompetence) of volunteers healthy.

To determine the effectiveness of echinacea extracts in preventing the development of cold symptoms, a meta-analysis of studies of this drug in experimental rhinovirus infection was performed. The main endpoint was the development of a clinically expressed cold, the secondary was the difference in the assessment of the common severity of cold symptoms between treatment groups, which was performed daily based on 8 symptoms of a cold, noted from 0 (absence) to 4 (very pronounced). When searching the medical research databases, only 3 studies of adequate design for the study of experimental rhinovirus infection were identified, which were included in the meta-analysis. It was found that the probability of developing clinically pronounced rhinovirus infection (colds) was 55% higher in the placebo group than in the echinacea group (risk ratio 1.55; 95% CI 1.02-2, 36, p less than 0.043). The absolute difference on the common severity scale for cold symptoms was -1.96 (95% CI -4.83-0.90; the differences were not statistically significant).

Thus, this meta-analysis suggests that standardized echinacea extracts are effective in preventing the onset of cold symptoms in experimental rhinovirus infection studies.