In the 10 vaccinated subjects (23–39 years), sampled 28 days post-primary COVID-19 mRNA vaccination and with no evidence of previous SARS-CoV-2 infection, frequencies of IFN-ɣ+ T cells reactive to the “Omicron S1/S2 pool” were slightly reduced compared with the “WT S1/S2 pool” (respectively, 22 median spot-forming units (SFU)/2.105 PBMCs) versus 26 SFU/2.105 PBMCs; p = 0.018). The gene discussed is IFNA1; the disease is COVID-19.