CD79A and selective IgA deficiency disease: Anti-spike IgA levels were significantly higher in oPAD patients or healthy controls after vaccination as compared to values obtained in unvaccinated individuals, but there was a trend towards lower levels in oPAD patients as compared to healthy controls (IgA anti-spike, median ratio: HC 9.10; oPAD 3.25), and seven oPAD patients failed to produce any IgA antibodies, including two patients with IgA deficiency (Figure 2B).