Probiotics for the Prevention of Upper Respiratory Tract Infections.

Narrative: Most treatments of URTI aim to control symptoms, because URTIs tend to self-remit in a few days to a week. It has been suggested that certain probiotic agents have the potential to prevent and mitigate URTI through immune-modulating properties. This Cochrane review examined 12 randomized trials (n = 3,720) of probiotics vs. placebo to prevent URTI.1 Included trials variably enrolled healthy children, adults, and older adults, while excluding trials examining persons at low risk (competitive athletes) and high risk (children prone to otitis). The studies demonstrated a reduction in episodes (number needed to treat to prevent one URTI = 8 during at least three months of treatment) and duration of URTI (mean difference = –1.89 days; 95% confidence interval [CI], –2.03 to –1.75). However, the rate ratio of URTI in patients exposed to probiotics compared with placebo was not significant (0.83; 95% CI, 0.66 to 1.05), suggesting that the number of URTIs was not affected overall. One low-quality trial suggested probiotics may reduce cold-related absences from work or school. Adverse effects were minor, with no statistically significant difference between groups.