To highlight, S. salivarus, which is increased in severe COVID-19 patients, seems to reduce colonic α- diversity and decrease T helper (Th) cells related cytokines or transcription factors, namely IFN-γ (Th1), GATA-3 (Th2) and TGF-β (Treg) in mouse pups (Li et al., 2022). Here, TGFB1 is linked to COVID-19.