Indirect evidence: transforming growth factor TGF-β, tumor necrosis factor TNF-α, and interleukin IL-6 were elevated in lung tissues, and the therapeutic value of two drugs (Pirfenidone and Nintedanib) for idiopathic pulmonary fibrosis in COVID-19-induced pulmonary fibrosis. Here, IL6 is linked to pulmonary fibrosis.