Diminished seroconversion following a single SARS-COV-2 vaccine in ocrelizumab-treated relapsing-remitting multiple sclerosis patients.

Background Despite impressive efficacy in immunocompetent individuals, the immunogenicity of a single dose of COVID-19 vaccine in B-cell-deplete patients remains unknown. Objectives We aimed to quantify real-world vaccine immunogenicity in ocrelizumab recipients. Methods We measured post-vaccination SARS-COV-2 immunoglobulin G (IgG) in ocrelizumab recipients using a highly sensitive Luminex assay. Results 44.1% of patients had detectable SARS-COV-2-IgG 21+ days after one vaccine dose, regardless of vaccine type (AZD1222 vs BNT162b2, odds ratio (OR) = 0.62, 95% confidence interval (CI) = 0.157-2.32, p = 0.72). B-cell count strongly predicted seroconversion (β1 = 12.38, 95% CI = 4.59-20.16, p = 0.0029), but undetectable B-cells did not preclude it. The second vaccine seroconverted 53% of the patients who had not already responded to dose 1. Conclusion Humoral response after one COVID-19 vaccine dose is lower than expected in CD20-deplete patients.