Supplementary Data — Probiotics reduce COVID-19 risk: real-time meta-analysis of 29 studies

October 2026

Probiotics COVID-19 outcomes

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Haran (RCT)67%0.33 · 0.01–8.16death0/1741/176 Haran (RCT)60%0.40 · 0.08–2.06hosp.2/1745/176 Haran (RCT)50%0.50 · 0.21–1.20hosp./ER/UC7/16915/181 Haran (RCT)20%0.80 · 0.61–1.04recov. time169 (n)172 (n) Gutiérre.. (DB RCT)35%0.65 · 0.53–0.80no recov.69/147105/146 Veterini29%0.71 · 0.41–1.22viral time15 (n)15 (n) Navarro-Ló.. (RCT)33%0.67 · 0.45–1.00no recov.14/2413/15 Navarro-Ló.. (RCT)53%0.47 · 0.20–1.08no recov.6/248/15 Navarro-Ló.. (RCT)20%0.80 · 0.65–0.98recovery24 (n)15 (n) Navarro-Ló.. (RCT)26%0.74 · 0.54–1.01recovery24 (n)15 (n) Hassan (RCT)80%0.20 · 0.02–1.65hosp.1/505/50 Hassan (RCT)18%0.82 · 0.56–1.21no recov.23/5028/50 Kolesnyk (DB RCT)60%0.40 · 0.18–0.90no recov.6/3416/36 Kolesnyk (DB RCT)21%0.79 · 0.63–0.98recov. time34 (n)36 (n) Kolesnyk (DB RCT)68%0.32 · 0.13–0.78PASC5/3416/35 Yamamoto (DB RCT)26%0.74 · 0.51–1.07no recov.45 (n)46 (n)PLATEAU Yamamoto (DB RCT)62%0.38 · 0.09–1.73viral+45 (n)46 (n)PLATEAU d'Ettorre87%0.13 · 0.01–2.33death0/284/42 d'Ettorre77%0.23 · 0.01–4.63ventilation0/282/42 d'Ettorre88%0.12 · 0.02–0.61progression28 (n)42 (n) Ceccarelli64%0.36 · 0.18–0.68death10/8834/112 Ceccarelli15%0.85 · 0.48–1.50ICU16/8824/112 Shah (RCT)11%0.89 · 0.75–1.06recov. time30 (n)30 (n)CT1 Shah (RCT)11%0.89 · 0.76–1.05hosp. time30 (n)30 (n)CT1 Shah (RCT)83%0.17 · 0.04–0.68no recov.2/3012/30CT1 Shah (RCT)4%0.96 · 0.80–1.16no recov.26/3027/30CT1 Li−12%1.12 · 0.74–1.69no disch.30/12341/188 Li−60%1.60 · 1.21–2.11no disch.123 (n)188 (n) Li−35%1.35 · 1.13–1.62viral time123 (n)188 (n) Zhang14%0.86 · 0.77–0.96hosp. time150 (n)150 (n) Zhang14%0.86 · 0.75–0.98recov. time150 (n)150 (n) Zhang17%0.83 · 0.75–0.93viral time150 (n)150 (n) Ceccarelli70%0.30 · 0.01–7.02death0/401/29 Ceccarelli82%0.18 · 0.02–1.54ICU1/404/29 Ivashkin (RCT)−2%1.02 · 0.26–3.97death4/994/101 Ivashkin (RCT)18%0.82 · 0.23–2.95ventilation4/995/101 Ivashkin (RCT)27%0.73 · 0.24–2.22ICU5/997/101 Ivashkin (RCT)5%0.95 · 0.84–1.08recov. time99 (n)101 (n) Zhang65%0.35 · 0.02–8.30ventilation0/251/30 Zhang67%0.33 · 0.10–1.05antibody3/2511/30 Saviano (RCT)67%0.33 · 0.01–7.95death0/401/40 Saviano (RCT)86%0.14 · 0.01–2.68ICU0/403/40 Saviano (RCT)26%0.74 · 0.30–1.83hosp. time40 (n)40 (n) Trinchieri78%0.22 · 0.03–1.93death1/213/14 Trinchieri78%0.22 · 0.09–0.55misc.4/2112/14 Trinchieri10%0.90 · 0.76–1.08misc.19/2114/14 Di Pierro (RCT)62%0.38 · 0.11–1.25death3/258/25 Di Pierro (RCT)0%1.00 · 0.45–2.24ICU8/258/25 Giancola (DB RCT)15%0.85 · 0.06–12.87death1/271/23 Giancola (DB RCT)33%0.67 · 0.30–1.48no recov.22 (n)20 (n) Giancola (DB RCT)−21%1.21 · 0.31–4.77no recov.4/223/20 Giancola (DB RCT)70%0.30 · 0.07–1.33no recov.2/226/20 Giancola (DB RCT)74%0.26 · 0.06–1.11no recov.2/227/20 Giancola (DB RCT)−14%1.14 · 0.56–2.30no recov.10/228/20 Louca8%0.92 · 0.85–0.99casespopulation-based cohort Di Pierro (RCT)98%0.02 · 0.00–0.33cases0/6424/64 Holt30%0.70 · 0.45–1.10cases20/909426/14,318COVIDENCE UK Ahanchian (DB RCT)73%0.27 · 0.03–2.25symp. case1/294/31 Ahanchian (DB RCT)85%0.15 · 0.01–2.73cases0/293/31 Fernánde.. (DB RCT)−2%1.02 · 0.06–16.09death1/981/100 Fernánde.. (DB RCT)−38%1.38 · 0.48–3.97recov. time10 (n)7 (n) Fernánde.. (DB RCT)−28%1.28 · 0.35–4.61severe case5/984/100 Fernánde.. (DB RCT)−2%1.02 · 0.37–2.80symp. case7/987/100 Fernánde.. (DB RCT)−35%1.35 · 0.53–3.44cases11/988/100 Wischme.. (DB RCT)33%0.67 · 0.38–1.17m/s case16/9124/91PROTECT-EHC Wischme.. (DB RCT)38%0.62 · 0.41–0.93symp. case24/9139/91PROTECT-EHC Wischme.. (DB RCT)27%0.73 · 0.37–1.45recov. time91 (n)91 (n)PROTECT-EHC Wischme.. (DB RCT)43%0.57 · 0.25–1.30cases8/9114/91PROTECT-EHC Rodrigue.. (DB RCT)9%0.91 · 0.12–6.70cases2/1272/128 Catinean40%0.60 · 0.41–0.88recovery60 (n)60 (n) Catinean38%0.62 · 0.42–0.93fever60 (n)60 (n) Di Pierro78%0.22 · 0.07–0.67cases186 (n)101 (n) Sarlin (DB RCT)33%0.67 · 0.11–3.98cases2/4133/414
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1 CT: study uses combined treatment
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← Probiotics
reduce risk
Probiotics
increase risk →
Fig. S1. All outcomes.
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Fig. S2. Comparison of results for RCTs versus observational studies. For COVID-19 treatments, there is no significant difference between the results of RCTs and observational studies. Observational studies do not systematically over or underestimate efficacy. For high-cost treatments, there is a non-significant trend towards RCTs showing greater efficacy.