Yeast Beta-Glucan Enhances Antibody Response Following Influenza Vaccination - A Double-Blind, Randomized, Placebo-Controlled Pilot Trial.

Yeast beta-glucans demonstrate immune-modulating effects; however, few studies have explored the potential of yeast beta-glucans to enhance immune response to vaccination. This pilot study aimed to assess the adjuvant effect of a yeast beta-glucan supplementation on antibody titer response to influenza vaccination. Adults ( = 90; 70.7 ± 10.1 years) were recruited over two vaccination seasons and randomized to receive 500 mg of beta-glucan or placebo (500 mg cellulose) daily in a double-blind study design. Pre- and 4 wk post-vaccination serum influenza-specific antibody titers were assessed using an optimized Hemagglutination Inhibition (HI) assay. Plasma cytokines 24 h post-vaccination were quantified by immunoassay. Cold and flu symptoms, using the Modified Jackson Criteria, fever, and self-perceived fatigue were monitored daily. Linear mixed models were used to test for differences in the fixed effects of time, treatment, and their interactions. In season 1 (Fall 2022), despite a baseline suggesting seroprotection for the Influenza A (H3N2 A/Wisconsin/67/2005) in 92% of the beta-glucan group and 74% of the placebo group, the post-vaccination antibody titer response (Δ = 95.8) favored beta-glucan over placebo ( = 0.037). Influenza B/Austria/1359417/2021 antigen demonstrated poor detection; 7 of the 10 HI detectible antibody responses seen were in the beta-glucan group. In season 2 (Fall 2023), the Influenza A (H1N1 A/Victoria/4897/2022) antigen demonstrated poor detection (14%), which precluded further cohort analyses. Of the cytokines, interferon-gamma (IFN-γ) increased similarly in both groups after vaccination, not supporting the adjuvant action of beta-glucan at the cellular level. Reported cold and flu symptoms were low in both groups and did not differ. Overall, the findings suggest that yeast beta-glucan supplementation may elicit a greater change in antibody titer to seasonal influenza vaccination. However, confirmation is needed with a larger sample of older adults and with follow-up to assess protection from disease. Clinical trial registry number and website: https://clinicaltrials.gov/study/NCT05074303.