A yeast-based product (EpiCor, a dried Saccharomyces cerevisiae fermentate) was compared to placebo to determine effects on the incidence and duration of cold and flu-like symptoms in healthy subjects recently vaccinated for seasonal influenza. In a 12-week, randomized, double-blind, placebo-controlled clinical trial, 116 participants received daily supplementation with 500 mg of EpiCor or placebo for 12 weeks. Data collected included periodic in-clinic examinations and serologic evaluations at baseline, 6- and 12-weeks. Subjects also utilized a standardized self-report symptom diary during the study. Participants receiving the yeast-based product had significantly fewer symptoms and significantly shorter duration of symptoms when compared with subjects taking a placebo.