Contrary to negligible S protein-specific antibody-based cross-reactivity, there is a likelihood of T cell cross-reactivity, as a minor proportion of healthy individuals; not previously exposed to SARS-CoV-2, have been found to possess SARS-CoV-2-specific reactive T cells, owing to a past infection with ‘common cold’ coronaviruses [130]. The gene discussed is PROS1; the disease is infection.