Background: The COVID-19 pandemic continues to pose unprecedented challenges to worldwide health. While vaccines are effective, supplemental strategies to mitigate the spread and severity of COVID-19 are urgently needed. Emerging evidence suggests susceptibility to infections, including respiratory tract infections, may be reduced by probiotic interventions. Therefore, probiotics may be a low-risk, widely implementable modality to mitigate risk of COVID-19 disease, particularly in areas with low vaccine availability and/or uptake. Methods: We conducted a randomized, double-blind, placebo-controlled trial across the United States testing the probiotic Lactobacillus rhamnosus GG (LGG) as post-COVID-19-exposure prophylaxis. We enrolled individuals > 1 year of age with a household contact with a recent (≤ 7 days) diagnosis of COVID-19. Participants were randomized to receive daily LGG or placebo for 28 days. Stool was collected to evaluate the microbiome. The primary outcome was development of symptoms of illness compatible with COVID-19 within 28 days. Findings: We enrolled 182 COVID-19-exposed participants. Intention-to-treat analysis showed that participants randomized to LGG were less likely to develop symptoms versus those randomized to placebo (26.4% vs. 42.9%, p=0.02). Further, LGG was associated with a statistically significant reduction in COVID-19 diagnosis (log rank p=0.049) via time-to-event analysis. Overall incidence of COVID-19 diagnosis was not significantly different between LGG (8.8%) and placebo (15.4%) (p=0.17). LGG was well-tolerated with no increased side effects versus placebo. Interpretation: These findings suggest that LGG probiotic may protect against the development of COVID-19 infection and symptoms when used as post-exposure prophylaxis within 7 days after exposure. Funding: This work was supported by a grant from the Duke Microbiome Center to A.D.S. and P.E.W. and private philanthropic donations to A.D.S. DSM/iHealth donated the LGG and placebo for the trial but had no role in its design, conduct, analysis, or writing. Trial registration: NCT04399252
Competing Interest Statement
P.E.W. has received unrestricted gift funding from DSM/iHealth and has a research grant from Abbott.
This work was supported by a grant from the Duke Microbiome Center to A.D.S. and P.E.W. and private philanthropic donations to A.D.S. DSM/iHealth donated the LGG and placebo for the trial but had no role in its design, conduct, analysis, or writing.
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
Ethics committee/IRB of Duke University gave ethical approval for this work
I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.
Paper in collection COVID-19 SARS-CoV-2 preprints from medRxiv and bioRxiv