In particular LF influences: (1) expression of pivotal biomarkers of COVID-19 like IL-6; (2) B-cell differentiation, total T-cell activation, T-helper cell activation and cytotoxic T-cell activation, (3) intestinal permeability strengthening the intestinal barrier function, (4) incidence and length of common and summer colds as an indication of an improved defense against viral infections in the respiratory tract, which again is also supported by (5) the effects of LF on the length and severity of symptoms in COVID-19 patients. Here, IL6 is linked to viral infectious disease.