IL6 and COVID-19: A systematic review and meta-analysis of published cytokine data from 25 studies (totaling 1245 patients) found that substantial differences existed in the levels of core pro- and antiinflammatory cytokines between patients with COVID-19 ARDS and non-COVID ARDS, revealing that levels of key mediators like IL-6 and TNF-α were often much lower in COVID-19 ARDS (18).