We describe the case of a 44-year-old female on Rituximab for treatment of multiple sclerosis with undetectable SARS-CoV-2 IgG specific antibodies eighteen days after second dose of SARS-CoV-2 vaccine. Interferon-gamma release assay testing for SARS-CoV-2 was positive on day nineteen, demonstrating robust T-cell mediated response despite lack of antibody-mediated response.