This clinical case history details a woman who received the COVID-19 vaccine BNT162b2 and developed an acute, severe encephalopathy associated with new onset seizures within days of her first vaccination. 

BNT162b2, an mRNA-LNP-vaccine, has been strategically purified and modified to suppress immunogenicity. It still possesses powerful intrinsic immune-stimulatory features that induce type-I INF production, which has been associated with both inflammation and potentially autoimmunity in several mRNA-vaccine phase-I/II clinical trials (HIV-NCT02413645, influenza-NCT03076385, rabies-NCT02241135 and Zika virus-NCT03014089).

A 69-year-old woman who received her first dose of BNT162b2 five days prior, was found unresponsive. Within twenty-four hours of arrival, she developed focal seizures with secondary generalized, and remained in non-convulsive status epilepticus on long-term EEG monitoring until day 5 of admission despite three anti-seizure medications and a propofol drip. 

Brain MRI on day 3 of admission showed gyriform-pattern diffusion restriction in the right hemisphere and left frontoparietal region without features suggestive of an acute vascular event. Vascular imaging was normal. Cerebrospinal fluid examination revealed an elevated protein level (135 mg/dl), with negative findings for infections from bacteria, fungi, mycobacteria, HIV, syphilis, and viruses, including COVID-19 PCR, as well as paraneoplastic and autoimmune encephalitis panels. Serum COVID-19 IgG antibody was negative on post-immunization day 8.  

There was no significant improvement following empiric methylprednisolone and meningitis antibiotic/antiviral treatment. She was discharged in a deeply comatose status on day 30 of hospital admission. Repeat MRI brain on day 14 showed similar findings to her previous scan with the addition of Wallerian degeneration in the right cerebral peduncle.   

In a patient who develops an acute encephalopathy with new onset of seizure within days of BNT162b2 vaccine, do consider mRNA-vaccine related encephalopathy in the differential diagnosis.