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Treating the Gut Microbiome Could Shorten Long COVID, Study Suggests


For reasons that aren’t entirely clear, long COVID is associated with diminished microbial diversity in the gut and a decrease in several healthful strains of bacteria, such as Bifidobacterium adolescentis. Researchers are now exploring whether therapies that aimed at reviving a beleaguered gut microbiome’s profile might be an avenue for treating long COVID.

Treating the Gut Microbiome Could Shorten Long COVID, Study Suggests image credit  gut bacteria ©Anatomy Insider/stock.adobe.com
©Anatomy Insider/stock.adobe.com

Last week researchers at The Chinese University of Hong Kong reported positive results for microbiome-modifying therapy in the journal The Lancet Infectious Diseases. Although randomized and double blinded, the study was conducted at a single center and so the findings must be interpreted with some caution.

Long COVID is also called long-haul COVID, post-COVID-19 conditions and chronic COVID. The technical term is post-acute sequelae of SARS-CoV-2 (PASC). Some research suggests that the proportion of people who develop long COVID after the initial infection has decreased. The National Center for Health Statistics reported in September 2023 that 6.9% of those who have had COVID-19 had had long COVID, according to the 2022 National Health Interview Survey.

Joint first authors Raphaela I Lau, PhD, and Qi Su and colleagues evaluated a preparation that included 3 strains of bacteria — Bifidobacterium adolescentis, Bifidobacterium bifidum and Bifidobacterium longum — and 3 compounds that encourage the growth of healthful bacteria: galacto-oligosaccharides, xylo-oligosaccharides and resistant dextrin. The study subjects had had at least 1 of 14 long COVID symptoms for 4 weeks or more after a confirmed infection with SARS-CoV-2 by either a PCR test or a rapid antigen test.

Between June 2021 and August 2022, the researchers randomly assigned 463 adults (mean age 49 years, men and women equally represented) to take either a placebo (vitamin C) twice daily or the bacteria-prebiotic preparation. The primary end point was the alleviation of long COVID symptoms by 6 months, defined as a reduction in the severity of symptoms leading to an improvement in activities of daily living. The symptoms were measured by responses to the PACSQ-14, a questionnaire commonly used in long COVID symptom research. After participant withdrawals and loss to follow-up, there were 204 individuals in the treatment group and 199 in the placebo group.


Results reported by Lau and Su and colleagues showed greater improvement among those in the treatment group vs those receiving placebo on all 14 long COVID symptoms. The results by proportion of patients whose long COVID symptoms were relieved:

Treating teh gut microbiome could shortren long covid, study suggests

The researchers also analyzed fecal samples and found greater diversity of bacteria diversity in the treatment group than in the placebo group. Their measurements also showed greater numbers of certain species (Bifidobacterium pseudocatenulatum and B. longum) and fewer of others (Klebsiella pneumoniae, Klebsiella variicola and Parabacteroides merdae). They also found association between the decreases in some symptoms with the bacteria; for example, B. adolescentis was positively associated with alleviation in fatigue.

“We found that SIMO1 led to improved gut microbiota composition by promoting the abundance of beneficial bacteria associated with [long COVID] such as those of the Klebsiella genus,” Lau and Su and colleagues wrote in their discussion. But they note that their analysis of cytokines didn’t show any difference between the treatment and placebo groups, so there are still unanswered questions about how improving the gut’s microbiota would ease long COVID symptoms.

Lau and Su also note one of the difficulties in researching long COVID: The symptoms are common, and many are nonspecific so teasing out the effect of a particular treatment and its effects.

This article originally appeared on our partner site Managed Healthcare Executive and has been lightly edited.

Source: Lau RI, Su Q, Lau IS, et al. A synbiotic preparation (SIM01) for post-acute COVID-19 syndrome in Hong Kong (RECOVERY): a randomised, double-blind, placebo-controlled trial. Lancet Infect Dis. Published online December 7, 2023. doi:10.1016/ S1473-3099(23)00685-0

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