CD79A and COVID-19: It has been noted that in adults, up to 20% of seronegative individuals had mucosal SARS-CoV-2 S-specific antibodies, some of which showed in vitro neutralizing capacity (37), and the authors suggested that S protein-specific IgA and IgG at mucosal sites, even in the absence of systemic responses, may be associated with mild COVID-19 and also with younger age.