Summary of selected systematic reviews and meta-analyses reporting on probiotics and respiratory infections
| Authors | Population | Included trials | Probiotic | Outcome | Effect |
| Vouloumanou et al 207 | Children and adults | 14 RCTs (3580 participants) | Any (mainly lactobacilli and bifidobacteria) | RTI | 4/10 RCTs reported probiotics reduced incidence of RTI 5/6 RCTs reported probiotics reduced severity of symptoms of RTI 3/9 RCTS reported probiotics shortened duration of RTI |
| Liu et al 208 | Critically ill adults | 12 RCTs (1546 patients) | Any | Nosocomial pneumonia | OR of nosocomial pneumonia with probiotics 0.75 (95% CI 0.57 to 0.97) No effect of probiotics on in hospital mortality, intensive care unit mortality, duration of hospital stay, duration of intensive care unit stay |
| Liu et al 209 | Children | 4 RCTs (1805 children) | Lactobacillus rhamnosus GG | RTI | RR of URTI with probiotics 0.62 (95% CI 0.50 to 0.78) RR for antibiotic treatment for URTI with probiotics 0.80 (95% CI 0.71 to 0.91) No effect of probiotics on LRTI or overall respiratory infections |
| King et al 210 | Children and adults | 20 RCTs (>4141 participants) | Any | RTI | SMD days of illness per person with probiotics −0.31 (95% CI −0.41 to −0.11); WMD days of illness with probiotics −0.77 (95% CI −1.50 to −0.04); SMD days of absence with probiotics −0.17 (95% CI −0.31 to −0.03) |
| Hao et al 211 | Children and adults | 13 RCTs; 12 RCTS in meta-analysis (3750 participants) | Any | URTI | OR of one URTI with probiotics 0.53 (95% CI 0.37 to 0.76) OR of at least three URTIs with probiotics 0.53 (95% CI 0.36 to 0.80) Mean duration of episode of URTI with probiotics −1.89 days (95% CI −2.03 to −1.75) OR for antibiotic prescription for URTI with probiotics 0.65 (95% CI 0.45 to 0.94) |
| Ozen et al 212 | Children | 14 RCTs | Any (mainly lactobacilli and bifidobacteria) | URTI | At least one beneficial effect of probiotics was observed in most of the RCTs |
| Araujo et al 213 | Children | 11 RCTs (2417 children) | Any | RTI | Several RCTs reports fewer new episodes, decreased duration of episodes and less severe symptoms |
| Wang et al 214 | Children | 23 RCTs (6269 children) | Any | RTI | RR of one RTI with probiotics 0.80 (95% CI 0.82 to 0.96); Days of RTI per child with probiotics −0.16 (95% CI −0.29 to 0.02) Days absent with probiotics −0.94 (95% CI −1.72 to −0.15) |
| Laursen and Hojsak215 | Children | 15 RCTs; 12 RCTs in meta-analysis (4527 children) | Any | RTI |
L. rhamnosus GG reduced duration of RTI −0.78 days (95% CI −1.46 to −0.090) Meta-analysis for other probiotics is not possible |
LRTI, lower respiratory tract infection; RCT, randomised controlled trial; RR, relative risk; RTI, respiratory tract infection; SMD, standardised mean difference; URTI, upper respiratory tract infection; WMD, weighted mean difference.