We show that COVID-19 continues to alter the immune system following virus clearance; (i) COVID-19 severity is characterized by abundant low-density neutrophils or high neutrophil-to-lymphocyte ratio persisting into convalescence, (ii) elevated levels of hyperactivated CD8+ T cells and proinflammatory non-classical monocytes were found in the blood among convalescent severe COVID-19 patients, and (iii) high values of HGF, VEGF-A and TNF-α are associated with COVID-19 severity leading into convalescence. This evidence concerns the gene HGF and COVID-19.