Variation in Antibody Titers Determined by Abbott and Roche Elecsys SARS-CoV-2 Assays in Vaccinated Healthcare Workers

SARS-CoV-2-specific antibody measurement is important for evaluating COVID-19 vaccine efficacy. We compared Roche, Abbott-IgG and Abbott-IgM antibody titres among SARS-CoV-2-naive healthcare workers following BNT162b2 vaccination. After the second dose vaccination, all samples tested positive for Roche and Abbott-IgG antibodies, with 83.6% Abbott-IgM positivity rate. Roche and Abbott-IgG antibody titers were correlated with age; their rate of decline was age-dependent in men. Abbott-IgG antibody titers decreased from 2 weeks after the second dose. Roche antibody titers peaked 2 weeks after the second dose in 76.2% of the participants; the titers recovered 3 months post-vaccination after declining at week 4 in 40.7% of the participants. The concordance between Roche and Abbott antibody titers over time was 47.5%. In conclusion, most participants presented significantly high Roche-S and Abbott-IgG(S) antibody titers after immunization. Some measurements were inconsistent with titer changes between these assays, possibly because of differences in immunoglobulin-specificity of the kits.