Fueled in part by Lee Stein’s early advocacy, the MACH-19 team at UC San Diego ran a randomized, double-blind, placebo-controlled trial showing that a capsule of Fomitopsis officinalis + Trametes versicolor mycelia (FoTv) taken with a COVID-19 shot is safe and practical as a vaccine add-on; the study reports that FoTv cut short-term post-jab side-effects in previously uninfected volunteers and preserved protective antibody levels for six months, pointing to a low-cost fungal strategy that could also help against future threats like H5N1.

Use of fungal mycelium as a vaccination adjunct may constitute a novel antiviral strategy to address newly emerging viruses. In a randomized, double-blind, placebo-controlled clinical trial, we evaluated safety and feasibility of fungal mycelium (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). We evaluated safety, feasibility, vaccine side-effects (across 5 days), and anti-SARS-CoV-2 Ab levels (across 6 months). Safety metrics were similar for the FoTv (N=52) and Placebo (N=38) groups and the approach was feasible. Participants with detectable Abs (from prior COVID antigen exposure) were classified as “COVID-Exposed” and those with undetectable Abs as “COVID-Naive.” FoTv, versus Placebo, significantly reduced side-effects in COVID-Naive, but not in COVID-Exposed individuals. In the COVID-Naive FoTv group, Ab responses were preserved across 6 months, an effect not observed among other groups. 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 an approach to prevent a novel pandemic virus (SARS-CoV-2), with potential application to H5N1/Bird Flu and other emerging viruses.