In this study, we investigated circulating IgA anti-SARS-CoV-2 S responses after vaccination and after a breakthrough infection (SARS-CoV-2 infection after receiving at least two COVID-19 vaccines) to better understand the impact of an Omicron breakthrough infection relative to vaccination on anti-SARS-CoV-2 S IgA levels. The gene discussed is CD79A; the disease is infection.