Faecalibacterium prausnitzii, whose abundance has been found to be negatively correlated with COVID-19 severity in adult patients (Zuo et al., 2020; Yeoh et al., 2021), has been found to both downregulate ACE2 in vitro and have immunomodulatory effects in vivo, leading to many considering it to be an attractive candidate for next generation probiotics (Cyprian et al., 2021; Ahmadi Badi et al., 2022; Martín et al., 2023). This evidence concerns the gene ACE2 and COVID-19.