Vaccine Response in People with Multiple Sclerosis Treated with Fumarates

People with multiple sclerosis (pwMS) have an increased risk of infection. As disease-modifying therapies (DMTs) and other treatments may interact with the immune system, there may be concerns about vaccine efficacy and safety. Therefore, it is important to evaluate possible interactions between DMTs and vaccines. The fumarates, dimethyl fumarate, diroximel fumarate, and monomethyl fumarate, are approved for the treatment of relapsing multiple sclerosis. This review assesses the evidence on vaccine response in pwMS treated with fumarates, with a particular focus on COVID-19 vaccines. Treatment with fumarates does not appear to result in blunting of humoral responses to vaccination; for COVID-19 vaccines, particularly RNA-based vaccines, evidence indicates antibody responses similar to those of healthy recipients. While data on the effect of fumarates on T-cell responses are limited, they do not indicate any significant blunting. COVID-19 vaccines impart a similar degree of protection against severe COVID-19 infection for pwMS on fumarates as in the general population. Adverse reactions following vaccination are generally consistent with those observed in the wider population; no additional safety signals have emerged in those on fumarates. Additionally, no increase in relapse has been observed in pwMS following vaccination. In pwMS receiving fumarates, vaccination is generally safe and elicits protective immune responses.