A natural fungal supplement, taken alongside COVID-19 vaccination, appears to reduce short-term side effects and may extend the durability of the antibody response, particularly in individuals who haven’t previously contracted the virus. The findings, published March 3, 2026, in BMC Immunology, offer a potentially promising adjunct to current vaccination strategies and could address concerns about vaccine hesitancy.
Researchers at the University of California San Diego School of Medicine conducted a randomized, double-blind, placebo-controlled clinical trial involving 90 adults receiving a COVID-19 vaccine. Participants were assigned to take either a four-day course of “FoTv”—a supplement derived from the mycelium (root-like structure) of the fungi Fomitopsis officinalis and Trametes versicolor—or a placebo, beginning on the day of their vaccination. The study focused on measuring safety, short-term side effects, and antibody levels over a six-month period. The concept of using natural products to enhance immune response isn’t new, but rigorous clinical testing at this scale is relatively rare.
“Natural products are widely used, but they are rarely tested at this level. We wanted objective data,” explained Gordon Saxe, MD, PhD, MPH, the study’s principal investigator and a professor in the Department of Family Medicine at UC San Diego School of Medicine. Many existing vaccines utilize synthetic immune adjuncts to boost antibody production, but these can sometimes arrive with an increase in unpleasant side effects like fever, chills, and muscle aches. The goal of this research was to identify a natural alternative that could strengthen vaccine protection without exacerbating these reactions.
Reduced Side Effects and Sustained Antibody Levels
The most significant results were observed in participants who were “COVID-naïve”—meaning they had never been infected with the virus and were unvaccinated at the start of the study. This group experienced significantly fewer side effects after vaccination when taking FoTv compared to those receiving the placebo. Perhaps more remarkably, antibody levels in the FoTv group continued to increase throughout the six-month study period, diverging from the typical pattern of an initial rise and subsequent decline.
“Antibody levels usually rise, peak about one month after vaccination, and then slowly decrease,” Saxe said. “In this group, we saw a significant decrease in vaccine side effects while, remarkably, antibody levels continued to increase up to the six-month mark.” Researchers found FoTv to be safe, with no adverse events reported during the trial.
The Potential of Fungal Mycelium as an Immune Modulator
The use of fungal mycelium as a potential immune booster stems from a growing understanding of the complex relationship between humans and fungi. Humans and fungi share a common evolutionary ancestor, and human immune cells possess receptors that interact with compounds found in fungi. This suggests that fungi like Fomitopsis officinalis and Trametes versicolor may contain compounds with untapped medicinal potential.
The researchers emphasize that fungal mycelium can be cultivated using standardized, scalable, and medical-grade production methods, making it a potentially viable option for preparing for future infectious disease outbreaks. This is particularly relevant given the ongoing threat of emerging pathogens like H5N1 avian influenza, commonly known as “bird flu.”
“With emerging infectious threats such as H5N1 avian influenza on the horizon, we require affordable and rapidly scalable tools that can strengthen vaccines without increasing their side effects,” Saxe stated. “This study shows that FoTv, a carefully tested natural immune modulator, may help support that goal.”
Implications for Vaccine Hesitancy and Future Research
The findings suggest that a natural supplement capable of reducing vaccine side effects while simultaneously enhancing antibody durability could play a role in addressing vaccine hesitancy. Reducing the discomfort associated with vaccination might encourage more people to get vaccinated, contributing to broader population immunity. Extending the duration of antibody protection could potentially reduce the frequency of booster shots.
The mushroom mycelium used in the study was provided by Fungi Perfecti, LLC of Olympia, Washington. The research was funded, in part, by grants from the University of California San Diego Krupp Endowed Fund, the Jonathan and Kathleen Altman Foundation, Fungi Perfecti, LLC, the Sacharuna Foundation, the Jesy Foundation, and Texas Instruments Foundation. Saxe disclosed that he serves on the board of the Krupp Endowed Fund but was recused from decision-making regarding this specific grant award.
While these initial results are encouraging, Saxe stressed the need for further research to confirm the findings and fully elucidate the mechanisms by which FoTv exerts its effects. The full study is available in BMC Immunology.
Disclaimer: This article reports on scientific research and is for informational purposes only. It’s not intended to provide medical advice. Consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
The researchers plan to continue investigating the potential of FoTv and other natural compounds as vaccine adjuvants. The next steps involve larger-scale clinical trials and a deeper exploration of the specific compounds within the fungal mycelium responsible for the observed immune-modulating effects. Readers interested in learning more about the study and future research can follow updates from the University of California San Diego School of Medicine.
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