Polypore mushroom mycelia as an adjunct to COVID-19 vaccination: a randomized clinical trial

Use of fungal mycelium as a vaccination adjunct may constitute a novel antiviral strategy to address newly emerging viruses. We evaluated safety and feasibility of a fungal mycelium-based natural product (Fomitopsis officinalis and Trametes versicolor, FoTv) as an adjunct to human COVID-19 vaccination, as well as its impact on vaccine side-effects and anti-SARS-CoV-2 antibodies (Abs). Randomized, double-blind, placebo-controlled clinical trial involving adjunctive treatment with FoTv or visually-identical Placebo (dosage: eight 500-mg capsules TID orally for four days) in combination with COVID-19 vaccination. Main outcomes included: Safety (adverse events, renal and hepatic function [Days 1–14]); Feasibility (completion rate and treatment adherence); Side-effects (number and severity, self-reported on days 1 [vaccination] to 5); and anti-SARS-CoV-2 Ab levels (receptor-binding domain and Spike, collected from blood drawn on days 1, 3, 14, and 28/42, and at 6 months). Ninety participants receiving COVID-19 vaccination were randomized to either FoTv (N = 52) or Placebo (N = 38) groups. There were no adverse events and the groups had overlapping 95% confidence intervals for the percentage of participants transitioning from normal to abnormal renal/hepatic function when comparing Days 1 and 14. All participants (100%) completed the study and treatment adherence was greater than 95%. Participants with detectable anti-SARS-CoV-2 Abs (from prior COVID antigen exposure) were classified as “COVID-Exposed” and those with undetectable anti-SARS-CoV-2 Abs as “COVID-Naive.” FoTv, versus Placebo, significantly reduced side-effects in COVID-Naive individuals, specifically on days 3 and 5, but not in COVID-Exposed individuals. In the COVID-Naive FoTv group, Ab responses were preserved across 6 months (and possibly increased), an effect not observed among other groups. After COVID-19 vaccination, adjunctive FoTv was safe, feasible, and reduced vaccine side-effects without compromising (and possibly increasing) Ab levels up to 6 months in participants without previous SARS-CoV-2 exposure. Use of fungal mycelia was successfully tested as a unique approach to prevent a novel pandemic virus (SARS-CoV-2), with potential application to H5N1/Bird Flu and other emerging viruses. Trial registered on ClinicalTrials.gov NCT04762628 on June 30, 2021.