Neutralizing antibody levels against SARS-CoV-2 variants of concern Delta and Omicron in vaccine breakthrough-infected blood donors.

Background: Novel SARS-CoV-2 variants of concern (VOC) Delta and Omicron are able to escape some monoclonal antibody therapies, making again COVID-19 convalescent plasma (CCP) a potential frontline treatment.

Study Design/methods: In this study, we investigated the kinetics of anti-SARS-CoV-2 neutralizing antibodies (nAbs) against VOCs Delta and Omicron in vaccine breakthrough infected plasma donors. Serum samples from 19 donors were collected at the time of plasma donation and tested for anti-SARS-CoV-2 nAbs (using live authentic VOC viral neutralization test) and IgG (Liaison® SARS-CoV-2 S1/S2 and Liaison® SARS-CoV-2 TrimericS IgG assays, DiaSorin). Measures were correlated with different variables, including the time between last vaccine dose and CCP donation, and time between SARS-COV-2 infection and CCP donation.

Results: nAb titers against VOC Delta and Omicron were directly related to the time interval since last vaccine dose to CCP donation, but inversely related to time since COVID19 breakthrough infection.

Discussion: SARS-CoV-2 breakthrough infection in vaccinated in donors boosts nAb titers against VOCs Delta and Omicron, but such titers decay shortly after infection. Therefore, CCP must be collected early after vaccine breakthrough infection.