Summarized together, trained immunity effects induced by microbial products (such as BCG, β-glucans, and lipopolysaccharides) are accompanied by a more effective cytokine response, which could lead to improved antiviral protection, even from the coronavirus disease, COVID-19 [110] (for a review, see Netea et al. 2020 [111]). This evidence concerns the gene PPIB and COVID-19.