IL6 and respiratory failure: Among these cytokines, IL-6 is an essential member of the pro-inflammatory cytokine family, inducing various proteins correlated with acute inflammation.200 In addition, the hyper-inflammatory syndrome of COVID-19 was reported to mainly involve IL-6.201 IL-6 was deemed as an indication of respiratory failure in hospitalized COVID-19 patients.202 Besides, another research indicated that severe COVID-19 symptoms are positively correlated with IL-6 levels.