Imagine a natural supplement that could make your COVID-19 vaccine work even better, with fewer side effects. Sounds too good to be true, right? But groundbreaking research from the University of California San Diego School of Medicine suggests this might be possible. A recent study found that a fungal supplement, taken alongside the COVID-19 vaccine, not only reduced short-term side effects but also helped antibodies—our body’s immune warriors—last longer in people who hadn’t been exposed to the virus before.
Published on March 3, 2026, in BMC Immunology, this randomized, double-blind, placebo-controlled clinical trial tested a four-day oral supplement called "FoTv." Derived from the mycelium (the root-like network) of two medicinal fungi—Fomitopsis officinalis and Trametes versicolor—FoTv was given to participants on the same day they received their vaccine. And this is the part most people miss: natural products like these are widely used globally but rarely undergo rigorous clinical testing. "Natural products are everywhere, but we often lack the objective data to back their claims," said Dr. Gordon Saxe, the study’s lead investigator and a professor in the Department of Family Medicine at UC San Diego School of Medicine.
Modern vaccines often rely on immune adjuncts—substances that boost antibody production. However, many of these are synthetic and can increase side effects like fever, chills, and muscle aches. But here’s where it gets controversial: could a natural immune regulator like FoTv offer a safer alternative? The study aimed to find out if FoTv could reduce side effects while maintaining or even enhancing antibody levels and vaccine protection.
The trial involved 90 adults who received either FoTv or a placebo for four days starting on their vaccination day. Researchers tracked safety, side effects, and antibody levels for up to six months. The results? FoTv was safe, with no adverse events reported. The most striking findings were in "COVID-naïve" participants—those who had never had COVID-19 or been vaccinated before. This group experienced significantly fewer side effects and saw their antibody levels continue to rise for six months, a stark contrast to the typical decline after one month.
"This is remarkable," Saxe noted. "Not only did we see fewer side effects, but antibody levels kept increasing, which is highly unusual." The researchers believe this could address vaccine hesitancy and reduce the need for frequent boosters. But here’s the bigger picture: fungal mycelium can be produced at scale using standardized, medical-grade methods, making it a promising tool for future infectious disease outbreaks, including threats like H5N1 avian influenza.
"With emerging threats like bird flu, we need affordable, scalable solutions to strengthen vaccines without adding side effects," Saxe explained. "FoTv, as a natural immune modulator, shows incredible potential. Humans and fungi share a common evolutionary ancestor, and our immune cells have receptors that respond to fungal compounds. We’re only beginning to scratch the surface of what fungi like FoTv can do."
Of course, more research is needed to confirm these findings and understand how FoTv works. But the implications are exciting. What do you think? Could natural supplements like FoTv revolutionize how we approach vaccines and immune health? Let us know in the comments—we’d love to hear your thoughts!
For the full study, visit: https://link.springer.com/article/10.1186/s12865-026-00809-9.
The study was funded by the UC San Diego Krupp Endowed Fund, Jonathan and Kathleen Altman Foundation, Fungi Perfecti, LLC, Sacharuna Foundation, Jesy Foundation, and Texas Instruments Foundation. The FoTv supplement was provided by Fungi Perfecti, LLC. The authors declared no competing interests, though Saxe serves on the Krupp Endowed Fund board and was recused from grant decision-making.
