Effect and Tolerability of a Nutritional Supplement Based on a Synergistic Combination of β-Glucans and Selenium- and Zinc-Enriched Saccharomyces cerevisiae (ABB C1(R)) in Volunteers Receiving the Influenza or the COVID-19 Vaccine: A Randomized, Double-Blind, Placebo-Controlled Study

A single-center, randomized, double-blind, placebo-controlled study was conducted in 72 volunteers who received a synergistic combination of yeast-based ingredients with a unique beta-1,3/1,6-glucan complex and a consortium of heat-treated probiotic Saccharomyces cerevisiae rich in selenium and zinc (ABB C1(R)) or placebo on the next day after getting vaccinated against influenza (Chiromas(R)) (n = 34) or the COVID-19 (Comirnaty(R)) (n = 38). The duration of treatment was 30 and 35 days for the influenza and COVID-19 vaccine groups, respectively. Mean levels of CD4+T cells increased from 910.7 at baseline to 1000.2 cells/mu L after the second dose of the COVID-19 vaccine in the ABB C1(R) group, whereas there was a decrease from 1055.1 to 929.8 cells/mu L in the placebo group. Changes of CD3+T and CD8+T lymphocytes showed a similar trend. In the COVID-19 cohort, the increases in both IgG and IgM were higher in the ABB C1(R) supplement than in the placebo group. Serum levels of selenium and zinc showed a higher increase in subjects treated with the active product than in those receiving placebo. No serious adverse events related to ABB C1(R) or tolerance issues were reported. The study findings validate the capacity of the ABB C1(R) product to stimulate trained immunity.