Effects of probiotic Lactobacillus brevis KB290 on incidence of influenza infection among schoolchildren: an open‐label pilot study

We investigated the efficacy of dietary consumption of Lactobacillus brevis KB290 (KB290) against influenza in humans by a preliminary intervention study on elementary schoolchildren, using a commercially available probiotic drink. Subjects were divided into Groups A and B, and an open‐label, parallel‐group trial was conducted in two 8‐week periods at a 1‐month interval in winter 2013/2014. Group A was provided with a bottle of the test drink containing KB290 (about 6 billion colony‐forming units) every school day in the first period and had no treatment in the second period, and vice versa for Group B. Epidemic influenza was not observed during the first period and only two of 1783 subjects were diagnosed. In the second period, the incidence of influenza in Groups A (no treatment) and B (provided the test drink) was 23·9 and 15·7%, respectively, and the difference was statistically significant (P