Published on Mar. 3, 2026
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A small clinical trial in San Diego found that a supplement made from the root-like networks of two mushroom species, Fomitopsis officinalis and Trametes versicolor, significantly reduced side effects from COVID-19 vaccines in participants who had no prior exposure to the virus. The supplement also appeared to boost antibody production in this group, with levels continuing to rise for up to six months after vaccination, unlike the placebo group. The researchers believe the fungal compounds may increase production of an immune-regulating molecule that tamps down acute inflammation while still allowing for the development of long-term memory cells.
Why it matters
The findings suggest a potential solution to the vaccine hesitancy problem, as a supplement that could reduce side effects while enhancing immunity could encourage more people to get vaccinated. If the results hold up in larger trials, such a supplement could also mean fewer booster shots would be needed over time.
The details
The study enrolled 90 adults in San Diego and had them take either the mushroom supplement or a placebo for four days starting on the day of their COVID-19 vaccination. The supplement contained freeze-dried mycelium from the Fomitopsis officinalis and Trametes versicolor mushroom species. In the ‘COVID-naïve’ group with no prior virus exposure, the supplement significantly reduced side effects reported on days 3 and 5 after the vaccine. This group also showed an unusual antibody trajectory, with levels continuing to rise for up to six months, unlike the placebo group and participants with prior COVID exposure.
The study was published on March 3, 2026.Participants took the supplement or placebo for four days starting on the day of their COVID-19 vaccination.
The players
Gordon Saxe
The study’s principal investigator and a professor of family medicine at UC San Diego.
Fungi Perfecti
The company that manufactures the mushroom supplement used in the trial and provided financial support and the capsules.
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What they’re saying
“Natural products are widely used, but they are rarely tested at this level. We wanted objective data.”
— Gordon Saxe, Principal Investigator (scienceblog.com)
“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.”
— Gordon Saxe, Principal Investigator (scienceblog.com)
What’s next
Larger clinical trials are needed to further investigate the potential of this mushroom supplement to reduce vaccine side effects and enhance long-term immunity, including measuring neutralizing antibodies and immune cell markers.
The takeaway
This small trial suggests a natural, affordable supplement derived from mushrooms could help address vaccine hesitancy by mitigating side effects while potentially boosting the body’s long-term defenses against COVID-19, offering a promising new approach to strengthening vaccine efficacy.
