the placebo effect...
so many sheeple have convinced themselves that it works, despite overwhelming evidence to the contrary; or think their covid symptoms were lessened after taking vaccine even though none of them had covid without the vaccine...
the irony is that about the only thing the vaccine (which isn't really a vaccine) accomplished was demonstrating how easily the masses can be manipulated into believing fallacies; many would probably even eat a turd if the media tried to convince them it was good for them...