Yellow fever vaccination in multiple sclerosis: A retrospective single-centre case series

To describe the clinical outcomes and safety of yellow fever vaccination (YFV) in patients with multiple sclerosis (MS) and the management of YFV according to the different disease modifying therapies (DMTs) around vaccination.

Single-center retrospective observational study conducted at the Pitié-Salpêtrière hospital, Paris. All patients who followed for a central nervous system demyelinating disease and who received YFV between 2019 and 2024 were included.

Twenty-six patients were included: 25 with MS and one with MOG-antibody-associated disease (MOGAD). Median age at vaccination was 34.5 years (range 22-58), and 21/26 (80.8%) were women. Two patients with relapsing-remitting MS experienced a clinical relapse within six months after YFV; both also had radiological activity. Brain MRI within six months after vaccination was available for only 8 patients; therefore the remaining patients could not be classified as free of radiological activity. Travel was the main reason for vaccination in 24/26 patients (92.3%): 17/26 (65.4%) had already planned a travel and 7/26 (26.9%) were vaccinated in anticipation of future travel, before the introduction of an immunosuppressive therapy. In the remaining 2 patients, YFV was a catch-up vaccination before the introduction of an immunosuppressive drug. No serious adverse event was documented in the medical records.

No unexpected safety signal was identified in this small retrospective cohort pf patients with MS. Two relapses occurred after YFV in patients with potential confounding factors, including treatment interruption, MS activity before YFV and the postpartum period.