A systematic review of 38 original studies measuring specific IgA reported a seroprevalence of 86.5% among PCR positive SARS-CoV-2 patients and that the production of specific IgA was detectable during the first 10 days following infection, and remained detectable for prolonged periods (e.g. 75 days after symptom onset).39 Finally, a study that analysed 100 communities in Wuhan, China showed that the presence of specific IgA antibodies decreased rapidly over time, as for IgM, especially those infected but who were asymptomatic.40 This evidence concerns the gene CD79A and infection.