It is important to know exactly the difference in changes in C5aR1 levels at onset and in antibody, especially Immunoglobulin G (IgG), levels after recovery between severe and non-severe COVID-19 patients to reduce the severity of the disease and prevent reinfection with SARS-CoV-2 because C5aR1 levels show the degree of inflammation at onset and IgG levels show the extent of survival of the virus fragments after recovery [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]. Here, C5AR1 is linked to COVID-19.