Probiotics may help in the fight against COVID-19

Post-exposure prophylaxis with the probiotic Lacticaseibacillus rhamnosus GG (LGG) led to prolonged time to COVID-19 infection, reduced incidence of symptoms, and gut microbiome changes, but not overall incidence, a study suggests.

There is emerging data suggesting the potential of probiotics to prevent respiratory tract infections. [Nature 2017;548:407-412; Cochrane Database Syst Rev 2015;2:CD006895; Br J Nutr 2014;112:41-54] “[T]hus, probiotics may be a low-risk, low-cost, and easily implementable modality to reduce the risk of COVID-19,” said the researchers.

“In our study … those randomized to LGG had fewer symptoms and prolonged time to development of COVID-19 compared with those receiving placebo,” they said. “While there was a trend to decreased COVID-19 incidence in participants [on] LGG, it was not statistically significant.”

To evaluate the efficacy of LGG as prophylaxis ≤7 days post-COVID-19 exposure, 182 individuals (63 percent women) with household exposure to someone with confirmed COVID-19 diagnosed within ≤7 days were included in the study. They were randomized 1:1 to LGG capsules (containing ten billion colony-forming units of LGG) or placebo once daily for 28 days. [Clin Nutr 2024;43:259-267]

Those on LGG were significantly less likely to report any symptoms by day 28 (26.4 percent vs 42.9 percent; p=0.02) and had significantly prolonged time to onset of symptoms (p_{log rank}=0.006).

Among symptomatic individuals during the study period (n=77), 22 had laboratory-confirmed COVID-19. Time to COVID-19 diagnosis was significantly prolonged for LGG vs placebo recipients (p_{log rank}=0.049). While there was a trend towards reduced COVID-19 incidence among LGG recipients, the difference was not statistically significant (8.8 percent vs 15.4 percent; p=0.17).

Of those who reported at least one adherence timepoint (n=110), adherence did not differ between the LGG and placebo arms (p=0.82). There was no significant difference in the fraction of participants who attributed symptoms to LGG vs placebo (8.8 percent vs 23.1 percent; p=0.32), but the odds of stopping product use due to symptoms attributed to the product was lower with the former vs the latter (0 percent vs 5.5 percent; p=0.02).

In the microbiome analyses (260 stool samples from 106 participants), LGG recipients had a significantly greater abundance of L. rhamnosus compared with those on placebo. “[This suggests] that participants were adherent to study therapy and that microbial community structure differentiated in response to probiotic treatment,” the researchers explained.

Despite the lack of difference in α-diversity between the LGG and placebo arms, a significant difference was seen in the overall structure of the stool microbiota (ie, ß-diversity; p=0.001).

Vaccines remain first-line

Evidence shows a potentially significant role of the microbiome and dysbiosis in COVID-19 disease severity and development of long COVID. [Gut 2021;70:698-706; Gut 2022;71:544-552] Hence, studies assessing the role of probiotics and other methods of microbiome optimization are urgently needed, the researchers noted.

“[O]ur results lend credence to the notion that our symbiotic microbes may be valuable partners in the fight against COVID-19 and potentially other future pandemic diseases,” they said. “[But it is important] to note that vaccination should remain first-line in COVID-19 prevention.”

The researchers called for further evaluation of the role of probiotics in larger and vaccinated cohorts and in populations with severe COVID-19. A comparison between pre- and post-exposure prophylaxis with LGG probiotics in high-risk populations is also recommended.