Table 1 Examples of completed clinical trials evaluating the efficacy of probiotics or prebiotics in the treatment of COVID-19

Efficacy of Probiotics in Reducing Duration and Symptoms of COVID-19

• Dietary supplement: probiotics (2 strains 10 × 10⁹ UFC)

• Dietary supplement: placebo (potato starch and magnesium stearate)

Enrollment: 17

• CIUSSS de L’Estrie-CHUS Hospital, Sherbrooke, Quebec, Canada

NCT04621071

Study to Evaluate the Effect of a Probiotic in COVID-19

• Dietary supplement: probiotic

• Dietary supplement: placebo

Enrollment: 41

• Hospital Universitario del Vinalopó, Elche, Alicante, Spain

• Hospital Universitario de Torrevieja, Torrevieja, Alicante, Spain

NCT04390477

Efficacy of Intranasal Probiotic Treatment to Reduce Severity of Symptoms in COVID-19 Infection

• Dietary supplement: probiotic

• Dietary supplement: saline solution

Enrollment: 23

• Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, Quebec, Canada

NCT04458519

The Effect of Probiotic Supplementation on SARS-CoV-2 Antibody Response After COVID-19

• Dietary supplement: L. reuteri DSM 17938 + vitamin D

• Dietary supplement: placebo + vitamin D

Enrollment: 161

• Örebro University, Örebro, Örebro Län, Sweden

NCT04734886

Study to Investigate the Treatment Benefits of Probiotic Streptococcus

Salivarius K12 for Hospitalized Patients (Non-ICU) With COVID-19

• Drug: standard of care

• Dietary supplement: BLIS K12

Enrollment: 50

• King Edward Medical University Teaching Hospital, Lahore, Punjab, Pakistan

NCT05043376

Oral Probiotics and Secondary Bacterial Pneumonia in Severe

COVID-19

• Combination product: oral probiotics

• Other: oral placebo

Enrollment: 70

• University of Passo Fundo, Passo Fundo, RS, Brazil

NCT05175833

Live Microbes to Boost Anti-Severe Acute Respiratory

Syndrome Coronavirus-2 (SARS-CoV-2) Immunity Clinical Trial

• Dietary supplement: OL-1, standard dose

• Dietary supplement: OL-1, high dose

• Dietary supplement: placebo

Enrollment: 54

• Rutgers University, New Brunswick, New Jersey, United States

NCT04847349

Efficacy of Probiotics in the Treatment of Hospitalized Patients With Novel Coronavirus Infection

• Dietary supplement: probiotic

• Dietary supplement: placebo

Enrollment: 200

• I.M. Sechenov First Moscow State Medical University, Moscow, Russian Federation

NCT04854941

Efficacy of L. plantarum and P. acidilactici in Adults With SARS-CoV-2 and COVID-19

• Dietary supplement: probiotic

• Dietary supplement: placebo

Enrollment: 300

• Hospital General Dr. Manuel Gea Gonzalez, Mexico city, Mexico

NCT04517422

Effect of Lactobacillus on the Microbiome of Household Contacts

Exposed to COVID-19

• Dietary supplement: Lactobacillus rhamnosus GG

• Dietary Supplement: Lactobacillus rhamnosus GG placebo

Enrollment: 182

• Duke University, Durham, North Carolina, United States

NCT04399252

Effect of a NSS to Reduce Complications in Patients With

Covid-19 and Comorbidities in Stage III

• Dietary supplement: nutritional support system (NSS)

• Other: conventional nutritional support designed by hospital nutritionists

Enrollment: 80

• ISSEMYM “Arturo Montiel Rojas” Medical Center, Toluca de Lerdo, Mexico State, Mexico

NCT04507867