“The Omicron variant of SARS-CoV-2 presents a wide spectrum of neurological manifestations."

"Although there is an improvement in the survival rate of patients with COVID-19, the frequency of neurological manifestations increases."

"The occurrence of delirium, cerebrovascular diseases, and ischemic stroke results in higher mortality."

Covid itself causes cognitive impairment. From 2020, prior to Covid vaccination of any kind:

“In our cohort of COVID-19 patients neurologic manifestations were frequent, including cognitive impairment.”