Cross-sectional studies of HCV- and HIV-1-infected individuals and longitudinal studies in YFV vaccine recipients showed that frequencies of HLA-C*03:04/peptide-binding KIR2DL2/3+ NK cells in peripheral blood were not influenced by whether a study subject encoded for HLA-C*03, and were furthermore independent of the underlying viral infection and did not change following YFV vaccination. This evidence concerns the gene HLA-C and viral infectious disease.