• IFN-γ level was significantly higher in Severe CAP patients than non-severe CAP and healthy (29). • IFN-γ level increased in two patients during acute phase but decreased with time (30). • IFN-γ level increased, IP-10 level did not change in pneumonia group (31). • Significantly higher than the SARS-CoV-1 patients 42% patient had CAP (37). • No major difference found in IFN-γ level of CAP and normal patients (38). This evidence concerns the gene IFNG and susceptibility to pneumonia measurement.