Thus, upon infection with H7N9, individuals with these HLA alleles will need time to activate and amplify new primary CD8+ T cell responses to distinct H7N9 peptide variants rather than recalling T cell responses generated against seasonal influenza viruses, potentially resulting in longer time to recovery and greater risk of severe disease compared to individuals with pre-existing cross-protective CD8+ T cell memory. The gene discussed is CD8A; the disease is infection.