Low numbers of naïve T cells and lower TCR diversity against SARS‐CoV‐2 epitopes were also associated with severe COVID‐19 [40, 41], and lower frequencies of IFN‐γ‐ and IL‐2‐producing T cells in SARS‐CoV‐2 have been reported in vaccinated older individuals [42]. This evidence concerns the gene IFNG and COVID-19.