Antibodies against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) in individuals with and without COVID-19 vaccination: A method comparison of two different commercially available serological assays from the same manufacturer

Mueller, Thomas

BACKGROUND: We compared two serological assays from Roche Diagnostics in individuals with and without COVID-19 vaccination, namely the Elecsys Anti-SARS-CoV-2 assay (detecting antibodies against the nucleocapsid protein of SARS-CoV-2) and the Elecsys Anti-SARS-CoV-2 S assay (detecting antibodies against the spike protein of SARS-CoV-2). METHODS: With both assays, we analyzed 3033 serum samples collected from 2496 patients without COVID-19 vaccination. In addition, we studied 34 healthcare-workers who received two injections of the BNT162b2 COVID-19 vaccine from BioNTech/Pfizer three weeks apart and who had repeatedly determined their antibody response by both assays. RESULTS: In our cohort of patients without COVID-19 vaccination, 62.9% of all determinations were negative with both Roche assays and 31.5% were positive with both assays. In 5.6% of our cohort, however, there were discordant results with both assays (partly because initially discordant results of the two assays became concordantly positive over time). In the healthcare-workers with the COVID-19 vaccination, the results of the Roche anti-nucleocapsid assay remained negative throughout the observation period of 5 weeks after vaccination. The initially negative antibodies against the spike protein became positive with the Roche assay in all samples two weeks after the initial injection, and the serum concentrations of anti-spike antibodies increased constantly until 4–5 weeks after the initial injection. CONCLUSIONS: Here, we provide information on serological testing with the two Roche assays, which may be important for the application of the two assays in clinical routine. There are differences in the pattern of antibodies in individuals with and without COVID-19 vaccination.