They could try detecting the spike mRNA or the spike protein in the cells. If they're in brain or endothelial cells, that would mean it got there, why is it there, what other cell damage is in the area...... I don't know if they've developed those detection tests for tissue.
There really have been a ton of studies this year on COVID-19, but not vaccine reactions. I don't think we know any good markers yet.
They could try detecting the spike mRNA or the spike protein in the cells. If they're in brain or endothelial cells, that would mean it got there, why is it there, what other cell damage is in the area...... I don't know if they've developed those detection tests for tissue.