Similarly, a significantly higher percentage of SARS-CoV-2-specific IFN-γ positive CD4+ T cells was also observed in the SARS-CoV-2 single infection group (0.66 ± 0.01%) than in the IAV + SARS-CoV-2 (0.44 ± 0.01%, P < 0.001) and SARS-CoV-2 + IAV (0.30 ± 0.06, P < 0.0001) coinfection groups. Here, CD4 is linked to infection.