Post-vaccinal seronegative autoimmune encephalitis following recombinant zoster vaccination in two immunocompetent patients.

BACKGROUND: Varicella Zoster Virus (VZV) causes varicella as a primary infection and establishes latency in sensory ganglia. Reactivation in adults leads to herpes zoster (HZ). A highly effective recombinant zoster vaccine (Shingrix®) was recently developed to prevent HZ. While vaccine safety data is reassuring, we report two cases of post-vaccinal seronegative autoimmune encephalitis (AE) following the first dose of the Shingrix® vaccine. CASE 1: A 67-year-old male surgeon presented one week after receiving the vaccine with a one-day history of dizziness, fatigue, and insomnia, followed the next day by confusion, agitation, terrifying visual hallucinations, paraphasic errors, and echolalia. Brain imaging and cerebrospinal fluid (CSF) analysis were unremarkable. The CSF multiplex polymerase chain reaction (PCR) panel targeting 14 bacterial and viral pathogens associated with meningitis/encephalitis was negative. All known AE antibodies were also negative. The patient initially improved with empiric anti-meningitis/encephalitis therapy, including a two-day course of steroids but he relapsed shortly after stopping the steroids, necessitating re-admission. Pulse steroid therapy followed by plasmapheresis led to full recovery. CASE 2: A 50-year-old female pediatrician presented with acute confusion nine days after the Shingrix® vaccination. CSF analysis showed lymphocytic-predominant mild pleocytosis and elevated protein, but brain imaging was unremarkable. The CSF meningitis/encephalitis PCR panel and AE antibodies were negative. Pulse steroid therapy and plasmapheresis led to full recovery.

CONCLUSIONS: These two cases highlight the potential for AE following the administration of the Shingrix® vaccine and underscore the importance of prompt recognition and aggressive immunotherapy to prevent morbidity and mortality.