New insights into antibody levels against SARS-CoV-2 for healthcare personnel vaccinated with tozinameran (Comirnaty)

AIM: The aim of this study is to determine the levels of spike protein IgG and total antibodies in subjects vaccinated against SARS-CoV-2 (both infected and non-infected) and the titer evolution over time. In addition, we also addressed the performance of each of the included platforms in the study, as they are intended to measure antibody levels in naturally infected patients. MATERIALS AND METHODS: An observational study including 288 volunteer healthcare professionals vaccinated against SARS-CoV-2 (Comirnaty(™)) at the Andújar Alto Guadalquivir Hospital. Serum samples were obtained in September 2020 and 14 and 90 days after administration of the second dose. The following in vitro methods were used: Elecsys Anti‐SARS‐CoV‐2 N and Elecsys Anti-SARS-CoV-2 S (Roche, Germany) and EliA SARS-CoV-2-Sp1 IgG (Thermo Fisher Scientific, Germany). RESULTS: For the Elecsys S method at 1/10 dilution and for the EliA Sp1 IgG method at 1/5 dilution, 54% and 19% of samples were out of range, respectively. The vaccine activated a high humoral response– 0 to 3000 BAU/mL being the “normal titer range” in all volunteers. Patients vaccinated after COVID-19 exhibited higher total S antibody load values than non-vaccinated volunteers while showing the same response for S IgG isotype. Titers decreased up to 86% in the case of S IgG neutralizing antibodies. CONCLUSIONS: The characterization of human response to SARS-CoV-2 vaccines is still far from being completely elucidated. It is important to increase the methods dynamic range to study humoral response evolution in depth and decide whether booster doses or seasonal vaccination plans will be necessary to definitively control the pandemic.