[swader999]

As OP indicates, it can still bind to ACE-2 and that changes the way these cells behave. Peristalsis in your veins is changed when the endothelial cells which have ACE2 are hit with spike (vaccine origin or covid origin) for instance.

I think there's enough evidence out there that spike from vaccines circulate widely. I can dig it up if you want?

[manwe150]

You are welcome to look for evidence, but OP is also wrong about the spike protein being "fully functional" in the vaccine. The spike protein sequence was modified in many ways in creating the vaccine, including to prevent it from undergoing the conformal change upon encountering ACE2 which would normally then cause the virus to then enter a cell.

For a sample reference: https://journals.asm.org/doi/10.1128/JVI.00203-21