Table 1.

Clinical trials on the effect of consuming probiotics against COVID-19. The data is up-to-date as of 28 November 2021, retrieved from https://clinicaltrials.gov/. The search query was “condition or disease” = “covid19”, “other terms” = “probiotics.”.

No.	Identifier	Title	Treatment	Probiotic Strain	Number Enrolled	Status
1	NCT04517422	Efficacy and safety of Lactobacillus plantarum and Pediococcus acidilactici as co-adjuvant therapy for reducing the risk of severe disease in adults with SARS-CoV-2 and its modulation of the fecal microbiota: A randomized clinical trial	Once per day, administered for 30 days	Combination of 4 probiotic strains, including 3 Lactobacillus plantarum strains CECT30292, CECT7484, CECT7485, and Pediococcus acidilactici strain CECT7483	300	Completed
2	NCT04458519	Clinical study of efficacy of intranasal probiotic treatment to reduce severity of symptoms in COVID-19 infection	Twice per day, administered for 14 days	Lactococcus lactis W136	23	Completed
3	NCT04854941	Efficacy of probiotics (Lactobacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium longum subsp. infantis and Bifidobacterium longum) in the treatment of hospitalized patients with novel coronavirus infection	3 times per day, administered for 14 days	Combination of 4 probiotic strains, including Lactobacillus rhamnosus PDV 1705, Bifidobacterium bifidum PDV 0903, Bifidobacterium longum subsp. infantis PDV 1911 and Bifidobacterium longum PDV 2301	200	Completed
4	NCT04399252	A randomized trial of the effect of Lactobacillus on the microbiome of household contacts exposed to COVID-19	2 capsules per day, administered for 28 days	Lactobaciltus rhamnosus GG	182	Completed
5	NCT04734886	Exploratory study for the probiotic supplementation effects on SARS-CoV-2 antibody response in healthy adults	2 capsules per day, administered for 6 months	Lactobacillus reuteri DSM 17938	161	Completed
6	NCT05043376	A randomized, open-label, and controlled clinical trial to study the adjuvant treatment benefits of probiotic Streptococcus salivarius K12 to prevent/reduce lung inflammation in mild-to-moderate hospitalized patients with COVID-19	2 tablets per day, administered for up to 14 days	Streptococcus salivarius K12	50	Completed
7	NCT04366180	Multicentric study to assess the effect of consumption of Lactobacillus coryniformis K8 on healthcare personnel exposed to COVID-19	Once per day, administered for 8 weeks	Lactobacillus coryniformis K8	314	Ongoing