CD79A and infection: Another point that deserves to be mentioned was that the same group presented a positive correlation between the serum levels of specific IgG and IgA for SARS-CoV-2 antigens post-vaccination, which indicates that, in some volunteers, the production of IgG and IgA occurred concomitantly, a fact that could have been impacted by the previous natural infection by SARS-CoV-2, as it was suggested that pre-existing antibodies can negatively interfere with the ability to respond to repeated antigenic stimulation [52].