We conducted a retrospective review of 1,448 patients evaluated at our Myelitis and Myelopathy Center (2003-2025). Patients were included if they developed myelitis within 2 months following vaccination and did not meet 2017 McDonald criteria for multiple sclerosis at first clinic visit. Demographic, clinical, and paraclinical data were obtained. 

Eleven patients were included (55% male, 64% white) with majority (64%) having subacute symptom onset. Vaccines included pneumococcal (n=1), influenza (n=2), yellow fever (n=2), and COVID-19 (n=6). The median time from vaccination to symptom onset was 14 days (IQR 12-21). At symptom nadir, median modified Rankin Scale was 4 (range 1–4): five (45%) were wheelchair-dependent. Bladder dysfunction occurred in eight (73%) and severe constipation in six (55%). The majority had cerebrospinal fluid (CSF) pleocytosis and elevated protein. Oligoclonal bands were absent in nine (82%), while one showed CSF-restricted and one mirror band(s). All infectious PCRs were negative. All patients were negative for AQP4 antibodies, and MOG antibodies were negative in all nine patients tested. On initial spinal cord MRI, eight patients (73%) had a monofocal longitudinally extensive lesion, with a median length of 5 vertebral segments (IQR 1-10). The central cord was most often affected (55%), and enhancement occurred in four patients (36%) with root enhancement in two (18%).  Over a median follow-up of 2.9 years (IQR 1.5–3.9), there were no changes in diagnosis.

Post-vaccination myelitis is rare and accounts for only a small proportion of all myelitis cases. Careful evaluation and longitudinal follow-up are essential to exclude other causes and unmasking of relapsing conditions.