Long-term systemic and mucosal humoral response in SARS- CoV-2 vaccinated post-Covid-19 infected patients

Abstract Longitudinal serum samples, nasopharyngeal/nasal swabs and rectal swab samples were collected from eighty-nine individuals (median age 66 y) with SARS-CoV-2 PCR-positive test results at Linköping University Hospital. Samples were collected from the initial visit and thereafter for up to 2 years of follow-up. The presence of serum IgG and IgA against SARS-CoV-2 antigens (S1-spike, nucleocapsid, and NSP3) was analysed. Nasal and rectal swabs were tested for the presence of mucosal IgA against the outer envelope S1 spike and the nucleocapsid protein. Ninety percent of the participants were seropositive for SARS-CoV-2 recombinant proteins on Day 28 after study entry, and all (100%) were seropositive based on samples collected 2 months or later. Almost all (95%) developed serum SARS-CoV-2-neutralizing antibodies that were measurable from 6 to 24 months. The most common antibody responses (both serum IgG, mainly IgG1, and in nasal mucosa IgA) reacted with the S1-spike protein and the nucleoprotein. In samples collected from nasal tissues, IgA anti-S1 spike protein was mainly observed during 2 months of follow-up. In a subpopulation (18% of tested individuals), rectal IgA swabs showed the presence of anti-S1 spike IgA for 1 month of follow-up among the participants studied. .