Preliminary evidence of blunted humoral response to SARS-CoV-2 mRNA vaccine in multiple sclerosis patients treated with ocrelizumab

Objectives: Several concerns regard the immunogenicity of SARS-CoV-2 vaccines in people with multiple sclerosis (pwMS), since the majority of them is treated with immunomodulating/immunosuppressive disease modifying therapies. Here we report the first data on the humoral response to mRNA SARS-CoV-2 vaccine in a case series of 4 pwMS treated with ocrelizumab (OCR) as compared to a group of healthy subjects (HS). Methods: We collected serum samples at 0, 14, 21 days after the first dose and 7 days after the second dose of BNT162b2-mRNA-Covid-19 vaccine from 55 health-care workers and 4 relapsing pwMS on OCR, with no history of Covid-19 infection. Sera were tested using the LIAISON®SARS-CoV-2 TrimericS-IgG assay (DiaSorin-S.p.A.) for the detection of IgG antibodies to SARS-CoV-2 spike protein. The anti-spike IgGtiters were expressed in Binding Antibody Units (BAU), an international standard unit. Results: At baseline all subjects were negative for anti-spike IgG. Seven days after the second dose of vaccine all HS mounted a significant humoral response (geometric mean 2010.4 BAU/mL C.I. 95% 1512.7-2672) while the 4 pwMS showed a lower response (range <4.81-175 BAU/mL). Discussion: Humoral response to BNT162b2-mRNA-vaccine in pwMS treated with OCR was clearly blunted. Further data are urgently needed to confirm and expand these preliminary results and to develop strategies to optimize the response to SARSCoV-2 vaccines in pwMS on OCR.