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.”

Very comprehensive evaluation of known neurological damage from SarsCov2:

“The pathogenesis of neurological disorders caused by SARS-CoV-2 involves several mechanisms. First, SARS-CoV-2 could enter the brain through retrograde transmission & hematogenous routes & disrupt brain function & structure, thus causing or exacerbating neurological disorders…”