IL2 and COVID-19: Moreover, regarding the concern of the increased pro-inflammatory events and cytokine storm related to the severity of COVID-19, the Sinovac vaccine was safe and did not promote any alteration in the frequencies of CD3+, CD4+, or CD8 T cells nor of secretion of IFN-γ, TNF-α, IL-2, IL-4, IL-5, or IL-6 (Table 2) (40).