Anti-ST2 (eg, astegolimab), anti-IL-33 (eg, MEDI-3506), small-molecule ST2 inhibitors IL-33-ST2 axis, soluble ST2 GATA3+ regulatory T cells, ILC2, type 2 pneumocytes, IL-2 and IL-7-producing dendritic cells, IL-9 and IL-7-driven γδT17 cells, GM-CSF-producing T cells, neutrophils, endothelial cells, mast cells, and M2 macrophages Effective against virus-induced exacerbations of asthma, might restore antiviral interferon responses; effective in haemophagocytic lymphohistiocytosis and MAS-like models incorporating interferon deficiencies (resembling severe–critical COVID-19); might be effective at all stages of COVID-19; and has potential against obesity-related severe COVID-19 Complexity of IL-33 biology—eg, nuclear versus extracellular cytokine, full-length versus cleaved form, membrane versus soluble receptor (targeting ST2 over IL-33 seems safer); atheroprotective and cardioprotective roles hypothesised for IL-33; unclear whether suppression of proinflammatory Th1 and Th17 cells by anti-ST2 favours Th2 responses along with regulatory T cell expansion; however, inhibition of ILC2, M2 and type 2 pneumocytes should overall result in antifibrotic effects