Bifidobacterium animalis subsp. lactis fails to prevent common infections in hospitalized children: a randomized, double-blind, placebo-controlled study.

Randomized, double-blind, placebo-controlled trial in hospitalized children in Croatia. Eligible participants were older than 12 months, with an overall age range of 1-18 years, and 362 children were analyzed in the probiotic group and 365 in the placebo group.

Children in the active arm received Bifidobacterium animalis subsp. lactis BB-12 orally as a sachet mixed with water, at a dose of 10^9 colony-forming units per day, given every morning for the entire hospital stay. The sachet contained 1 g maltodextrin powder; the comparator was placebo.

B. animalis subsp. lactis BB-12 did not prevent nosocomial infections in hospitalized children. The primary endpoint was not significant: 29 infections in the intervention group versus 22 in placebo, incidence rate ratio 0.76, 95% CI 0.41 to 1.36, P = 0.32. Respiratory tract infection rates were also similar (IRR 1.08, 95% CI 0.45 to 2.59, P = 0.85), and gastrointestinal infection rates did not differ significantly (IRR 0.53, 95% CI 0.21 to 1.25, P = 0.11). No recurrent infections or adverse events were recorded.

The overall incidence of nosocomial infections was lower than expected, which reduces power to detect benefit. The trial was conducted in a single pediatric hospital setting during a relatively short hospitalization period, limiting generalizability. The null findings also apply to this specific strain and indication rather than probiotics as a class.