The Human Ecology Journal > Probiotics and COVID-19

Probiotics and COVID-19

In this newsletter, we would like to share our perspective, which is in line with expert opinions that came recently online such as:

ISAPP science blog – Can probiotics go viral?
By Prof. Glenn Gibson, Food Microbial Sciences Unit, Department of Food and Nutritional Sciences, The University of Reading, UK

Nature Microbiology – Can bacteria help humans fight COVID-19?
By Prof. Gregor Reid, Distinguished Professor of Microbiology and Immunology and Surgery at Western University, and the Endowed Chair in Human Microbiome and Probiotics at the Lawson Health Research Institute.

Microbe – Virus Interaction
Research on the antiviral potential of probiotic bacteria is still in its infancy as the molecular mechanisms by which bacteria can combat viruses remain largely unexplored. There is very little to no evidence that the microbiome or probiotics can directly decrease the infection rate of this highly infective COVID-19 virus. Therefore, it is expected that the effect of probiotics on the impact of this virus lies not within direct inhibition of the virus itself but by supporting the immune system in its fight against the virus1.

Microbiome – Immunity
However, the microbiome is known to influence the acquired immunity in various ways, for instance by activation and differentiation of T-cells through dendritic cells in the gut. The T-helper 1 cell (Th1) is essential for the immune response against viral infections, further supported by regulatory T-cells balancing the immune system generally.

The immune-modulating potential of probiotics is illustrated by studies on vaccination efficiency, which is an accepted model indicated by the European Food Safety Authority (EFSA) to substantiate a supplement or food health claim on the function of the immune system related to defense against pathogens in healthy individuals2. A systematic review in 2018 encompassed 26 RCT’s in humans, involving 3,812 participants, investigating the effect of 40 different probiotic strains on the response to 17 different vaccines. In about half of the studies, a beneficial effect of probiotics was reported. It is too early to draw final conclusions, mainly because of the variation between the studies in strain, dose, viability, duration, and timing. However, the authors conclude that probiotics offer a relatively cheap intervention to improve vaccine efficacy and duration of protection3.

Other examples where probiotics support the immune system can be found in the upper respiratory tract infections (URTI) field of research. Although also there is much heterogeneity present among studies, by using different products and making use of different setups, Glenn Gibson emphasizes the Cochrane group concluded that “probiotics were found to be better than placebo in reducing the number of participants experiencing episodes of acute URTI by about 47% and the duration of an episode by about 1.89 days”4.

The advice of China’s National Health Commission and National Administration of Traditional Chinese Medicine
There is no evidence that the modulation of gut microbiota plays a therapeutic role in COVID-19 patients. However, Gao et al. speculate that targeting the gut microbiota is of interest5. This is substantiated by the fact that Pan et al. described that of 204 COVID-19 patients analyzed in the epicenter Wuhan, more than half of the population reported digestive symptoms, including lack of appetite (majority), diarrhea, vomiting or abdominal pain, which indicates a link for the gut-lung interaction in this viral infections6. In addition, researchers from this area hypothesize that a dysfunctional gut-lung communication is mediated by angiotensin-converting enzyme 2 (ACE-2), the primary receptor for different coronaviruses, which is both present in the gut and lung epithelia. The potential role of the microbiota in COVID-19 infection was as well acknowledged in clinical practice. In facing the COVID-19 crisis, China’s National Health Commission and National Administration of Traditional Chinese Medicine recommended probiotics in the treatment of patients with severe COVID-19 infection, to maintain the microbial balance and prevent secondary bacterial infection5.


  1. 1. Miyauchi K. Helper T Cell Responses to Respiratory Viruses in the Lung: Development, Virus Suppression, and Pathogenesis. Viral Immunol 2017;30:421-30
  2. 2. EFSA. Guidance on the scientific requirements for health claims related to gut and immune function. EFSA Journal 2011;9.
  3. 3. Zimmermann P, Curtis N. The influence of probiotics on vaccine responses - A systematic review. Vaccine 2018;36:207-13.
  4. 4. Hao Q, Lu Z, Dong BR, Huang CQ, Wu T. Probiotics for preventing acute upper respiratory tract infections. The Cochrane database of systematic reviews 2011:Cd006895.
  5. 5. Gao QY, Chen YX, Fang JY. 2019 Novel coronavirus infection and gastrointestinal tract. J Dig Dis 2020.
  6. 6. Pan L, Mu M, Yang P, et al. Clinical characteristics of COVID-19 patients with digestive symptoms in Hubei, China: a descriptive, cross-sectional, multicenter study. preprint 2020.