Poop transplants are an unusual branch of medicine. Known as IStool transplant, or fecal microbiota transplants (FMT), they aim to boost the body’s immune response by introducing a healthy cast of microbes to the gut’s microbiome. The treatment involves donating some feces from one person to another by packaging some poop into a pill and letting them swallow it.

The donors are usually people you live in close proximity with as their gut microbiome will be armed with all the good bacteria that come in handy in your specific habitat. They’re given as a means of boosting someone’s immunity, often after their gut has lost its good bacteria due to illness or as a result of inappropriate medication (handy reminder to only use antibiotics when directed by a doctor).

Now, however, it appears FMTs may have a role to play in the fight against COVID-19 with researchers already planning a clinical trial. The novel approach comes in light of two reports of patients who both became infected with a stomach bug as well as COVID-19. They each received a fecal transplant and shortly after their symptoms for both illnesses rapidly disappeared. The small but curious findings were published in a letter in the journal Gut.

The first case involved an 80-year-old man who had been battling recurrent Clostridioides difficile and later succumbed to pneumonia as well as symptoms that were indicative of COVID-19. A swab test confirmed that the patient had tested positive and so they were treated with remdesivir and convalescent plasma containing antibodies to SARS-CoV2. They were also given a fecal transplant to combat the recurrent C difficile.

Surprisingly, shortly after the transplant the patient’s COVID-19 symptoms cleared up rapidly, and while other treatments were also given it’s not currently thought that either of them is effective in speeding up the recovery time from the disease.

The second case involved a 19-year-old who had ulcerative colitis and was being treated with immunosuppressants. They were also experiencing repeating episodes of C. difficile and so was given antibiotics and a fecal transplant to combat it. Shortly after, the patient developed COVID-19 symptoms and again a swab test confirmed that they were infected with the SARS-CoV-2 virus. However, their symptoms subsided without any treatment.

In both cases, the doctors were able to rule out that the patients had been infected with SARS-CoV-2 by the fecal transplants as they were tested for the virus before being given. What’s surprising is that both patients had risk factors for experiencing severe COVID-19 symptoms and yet neither became particularly ill with the disease. “[O]ne possible explanation being that [stool transplant] mitigated more adverse outcomes, potentially through impacting microbiome-immune interactions,” the authors said in a statement. 

The findings are by no means definitive as it can’t be confirmed that the poop pills were the deciding factor in their lessened disease severity and recovery. However, the researchers suggest it’s a worthy area of investigation building on scores of research into the benefits of this unusual therapy in the treatment of other illnesses.

“Our main conclusion from these cases is that [stool transplant] appears safe and of comparable efficacy in treating recurrent [C difficile infection] in patients with coexisting COVID-19,” they wrote. “These data let us speculate that gut microbiome manipulation may merit further exploration as an immunomodulatory strategy in COVID-19.”