The elevated reactogenicity to vaccination could be related to a general exaggerated response to antigens in this group (genetic differences) or a reflection of the immune response to a higher viral burden during SARS2 infection (a consequence of having more severe COVID-19) and somehow tied to the lower nasal/systemic IgA levels, though we could not find any evidence of this in past studies. This evidence concerns the gene CD79A and COVID-19.