IL6 and COVID-19: A systematic review and meta-analysis of seven studies, performed by Aziz and colleagues reported the mean of serum IL-6 in 56.8 pg/mL (41.4–72.3 pg/mL) for severe COVID-19 group [26], while both our group and Xu et al. found higher IL-6 values for severe and critical COVID-19 patients [12].