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Probiotics for preventing acute upper respiratory tract infections

Updated Cochrane review (2022) of 23 RCTs (n=6,950): probiotics versus placebo may lower URTI diagnoses (RR 0.76), recurrent URTIs (RR 0.59), antibiotic prescriptions (RR 0.58), and shorten episode duration (MD −1.22 days), with mostly low–moderate GRADE certainty.

Scope

Cochrane update of randomised trials comparing any specified probiotic strain/dose with placebo or no treatment to prevent acute upper respiratory tract infections across ages.

Included evidence

  • 23 usable RCTs, 6,950 participants (children through older adults)
  • Typical products: 1–2 strains, often 10⁹–10¹¹ CFU/day, >3 months exposure in many trials

Pooled intention-to-treat signals (abstract)

  • ≥1 URTI diagnosis: RR 0.76 (95% CI 0.67–0.87; P < 0.001; 16 trials, 4,798 participants; low-certainty)
  • ≥3 URTI episodes: RR 0.59 (95% CI 0.38–0.91; P = 0.02; 4 trials, 763 participants; moderate-certainty)
  • Incidence rate (cases/person-year): rate ratio 0.82 (95% CI 0.73–0.92; P = 0.001; 12 trials, 4,364 participants; low-certainty)
  • Mean episode duration: MD −1.22 days (95% CI −2.12 to −0.33; P = 0.007; 6 trials, 2,406 participants; low-certainty)
  • Antibiotic use for URTI: RR 0.58 (95% CI 0.42–0.81; P = 0.001; 6 trials, 1,548 participants; moderate-certainty)
  • Any adverse event: RR 1.02 (95% CI 0.90–1.15; P = 0.79; 8 trials, 2,456 participants; low-certainty)

Evidence hygiene

Strain-, matrix-, and dose-specific effects dominate real-world decisions—do not treat all yoghurts or capsules as equivalent to positive trial arms.

Publication

Zhao Y, Dong BR, Hao Q. Cochrane Database Syst Rev. 2022 Aug 24;8(8):CD006895. PMID 36001877.

Outcomes

  • Participants with ≥1 diagnosed acute URTI: pooled RR 0.76 (95% CI 0.67–0.87; P<0.001; low-certainty) for probiotics vs placebo or no treatment (16 trials, n=4,798).
  • Mean duration per acute URTI episode: pooled MD −1.22 days (95% CI −2.12 to −0.33; P=0.007; low-certainty) across 6 trials (n=2,406).
  • Participants using prescribed antibiotics for acute URTI: pooled RR 0.58 (95% CI 0.42–0.81; P=0.001; moderate-certainty) across 6 trials (n=1,548).
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