myelin oligodendrocyte glycoprotein (MOG) antibody syndrome associated with the Moderna COVID-19 mRNA vaccine, and a case of acute transverse myelitis (ATM) associated with the Pfizer COVID-19 mRNA vaccine.

Post-vaccination CNS demyelinating syndromes have been reported with different vaccines, most notably the influenza and human papilloma vaccines. Two cases of new-onset multiple sclerosis (MS) and a case of new-onset neuromyelitis optica (NMO) associated with the Pfizer vaccine have been reported. One case of new-onset relapsing-remitting MS was reported after the Moderna vaccine.

A 38-year-old man developed left blurry vision, lower extremity weakness/paresthesia and bowel/bladder dysfunction three days after receiving the Moderna vaccine. He was diagnosed with left optic neuritis and longitudinally extensive transverse myelitis; he tested positive for MOG antibody. A 39-year-old woman presented with progressive lower extremity weakness/numbness seven days after receiving the Pfizer vaccine. She was diagnosed with ATM. Both patients improved with intravenous corticosteroids.

The association between CNS demyelinating syndromes and vaccination has been reported for many years. The proposed pathogenesis of CNS demyelinating syndromes after vaccines includes molecular mimicry, epitope spreading, bystander activation, polyclonal activation, effects of adjuvants, and depends on vaccine-related factors like type, dose, and route of administration. The adjuvanticity of COVID-19 vaccines is novel in that it involves Toll-like Receptor (TLR) 7 and 9 agonism, and several immune-mediated disorders have been linked to altered nucleic acid metabolism and processing that have stimulated TLR-7 and TLR-9 experimentally.

While the risk of CNS demyelinating events is non-negligible, the incidence is very low. The rate of demyelinating events after the COVID-19 infection is higher. Therefore, we feel that the overall benefits of vaccination outweigh the marginal risk. However, providers should be aware of this potential neurological complication of the COVID-19 mRNA vaccines.