Summary
Across 107 trials (101,751 adults), multi-strain probiotics modestly lowered respiratory infection incidence (risk ratio 0.90, 95% confidence interval 0.82 to 0.98, moderate certainty), as did Bifidobacterium animalis (risk ratio 0.79) and catechin. The same analysis found high-dose vitamin D the most effective for COVID-19 or influenza (risk ratio 0.66).
Key points
- Design: network meta-analysis of randomized controlled trials, search to Feb 2025. Probiotic effects are small and strain-specific.
- Funding: none listed; authors declare no competing interests.
- Added from the October 2026 literature sweep, from the abstract; curators to check against the full text.