Multifocal meningoencephalitis after vaccination against COVID-19.

We report the case of an 84-year-old male patient who was transferred to our hospital because of impaired consciousness and high fever, and died about 10 weeks after his fourth "coronavirus disease 2019" (COVID-19) vaccination. Autopsy revealed acute ischemic change with microhemorrhage and perivascular T-cell infiltration in the thalamus, pons, and cerebellum, which were considered to be related to neurological symptoms. There were dilatation of the right ventricle, accumulation of pleural effusion, and ascites, suggesting right heart failure. Although the patient had a negative COVID-19 polymerase chain reaction test, immunohistochemical analysis for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens (spike and nucleocapsid proteins) was performed to identify the cause of death. Surprisingly, only SARS-CoV-2 spike protein was detected in the thalamus, pons, and pituitary and adrenal glands. The presence of SARS-CoV-2 spike protein might have been due to vaccination rather than viral infection, because no SARS-CoV-2 nucleocapsid protein was detected. The spike protein in the central nervous system might have been related to the acute ischemic change, and that in the pituitary and adrenal glands may have been associated with right heart failure, possibly through dysfunction of the renin-angiotensin-aldosterone system.