University California San Diego Study: Natural Fungal Supplement Reduces COVID-19 Vaccine Side Effects, Extends Antibody Duration
Researchers at University California San Diego School of Medicine conducted a study indicating that a natural fungal supplement, FoTv, taken during COVID-19 vaccination reduced short-term side effects and prolonged antibody duration in individuals who had no prior exposure to the virus.
The study, published March 3, 2026, in BMC Immunology, was a randomized, double-blind, placebo-controlled clinical trial. It investigated the effects of a four-day oral supplement derived from the mycelium of Fomitopsis officinalis and Trametes versicolor (FoTv). Participants began taking the supplement on the day they received their vaccine.
Study Objectives
Dr. Gordon Saxe, the study's principal investigator and a professor at UC San Diego School of Medicine, stated that the goal was to assess if FoTv could decrease vaccine side effects while preserving or increasing antibody levels and helping vaccine protection last longer.
The Search for Improved Immune Adjuncts
Many modern vaccines use immune adjuncts to help the body produce a stronger antibody response. While these often boost antibody production, they can also increase side effects such as fever, chills, fatigue, and muscle aches. The scientific community has been searching for an immune adjunct that can strengthen vaccine protection without increasing short-term side effects.
Trial Methodology and Safety
The study included 90 adults receiving a COVID-19 vaccine who were randomly assigned to take either FoTv or placebo capsules for four days, starting on the day of vaccination. Researchers measured safety, short-term vaccine side effects, and antibody levels at intervals up to six months. FoTv was found to be safe, with no adverse events reported.
Promising Results in COVID-Naïve Individuals
The strongest results were observed in participants who were "COVID-naïve," meaning they had never had COVID-19 and had not been vaccinated before joining the study.
In this group, those who took FoTv experienced significantly fewer side effects after vaccination compared with those taking the placebo. Additionally, antibody levels in COVID-naïve participants who took the supplement continued to increase over the six months of the study.
This contrasts with the typical pattern where antibody levels usually rise, peak about one month after vaccination, and then slowly decrease.
Potential Impact and Future Directions
The researchers noted that a natural supplement capable of decreasing side effects while improving antibody durability might help reduce vaccine hesitancy and potentially reduce the need for frequent booster shots.
Because fungal mycelium can be grown using standardized, scalable, and medical-grade production methods, researchers believe this approach could play a role in preparing for future infectious disease outbreaks, including activity against influenza A strains such as H5N1 ("bird flu").
Dr. Saxe emphasized that additional studies are needed to confirm these findings and to better understand how the supplement works. The study was supported by various grants, including from the University of California San Diego Krupp Endowed Fund and Fungi Perfecti, LLC.