Impact of mass vaccination on SARS-CoV-2 infections among multiple sclerosis patients taking immunomodulatory disease-modifying therapies in England.

Background: Contradicting assumptions have been made about the effectiveness of SARS-CoV-2 vaccines in patients with multiple sclerosis (MS) receiving immunomodulatory disease-modifying therapies (DMTs) based on the quantification of humoral and cellular immune responses. This study aimed to understand changes in the risk of SARS-CoV-2 infection among the total population of patients receiving MS DMTs in England following mass vaccination.

Methods: This is a retrospective analysis of national data collected prospectively and longitudinally. National Health Service (NHS) England and NHS Improvement (NHSE/I) hold prescribing data on all commissioned MS DMTs in England. United Kingdom Health Security Agency (UKHSA) has been collecting data on all registered SARS-CoV-2 test results, including polymerase chain reaction and rapid antigen tests. All patients receiving MS DMTs were identified using NHSE/I datasets. All patients receiving MS DMTs with SARS-CoV-2 infection (i.e., positive test) from March 2020 to August 2021 were identified by merging NHSE/I and UKHSA datasets. Similar data for the general population were captured using publicly available datasets of the United Kingdom government. The incidence rate ratios (IRR) of SARS-CoV-2 infection among patients receiving MS DMTs compared to the general population during the pre-vaccination (November 2020 to January 2021) and post-vaccination (June to August 2021) periods were calculated.

Results: A mean (standard deviation) of 41,208 (4,301) patients received an MS DMT in England during each month from March 2020 to August 2021. The IRR (95% confidence interval) of infection in patients taking ocrelizumab versus the general population increased from 1.13 (0.97-1.31) during the pre-vaccination period to 1.79 (1.57-2.03) during the post-vaccination period. For patients on fingolimod, it increased from 0.87 (0.73-1.02) to 1.40 (1.20-1.63) during the same periods. There were no significant changes for patients on other MS DMTs.

Conclusion: SARS-CoV-2 vaccines offer less protection against infection to patients taking ocrelizumab or fingolimod, who have an impaired immune response to vaccines, than the general population. These findings will have implications for vaccination policies.