CD4 and infection: A study evaluating phenotype, specificity, function, and persistence of nasal-resident SARS-CoV-2–specific T cells showed almost exclusive detection of SARS-CoV-2–specific CD4 and CD8 T cells in nasal mucosa among individuals with hybrid immunity versus those with only vaccine-induced immunity (18), with nasal-resident T-cell responses persisting for ≥140 days post infection (18).