Nothing is ever that simple, but of cases with effects consistent with the protein being in the blood stream with consequences to the heart and brain, if that were a factor, it would be both testable and avoidable, and provide the explanation people would need to choose to get the shot. If the odds of accidentally hitting a vein and the bloodstream consequences as described lined up, it could move the issue forward.

I have zero expertise in this area, my interest in asking is what would make a more compelling case for getting more people immune, and having a straightforward explanation for the causes of the prior reports of harm would go a long way toward that goal.

Put another way: would injecting directly into an artery or vein have risks that the intramuscular jab would not - and do those risks resemble the anecdotal reports of myo, clots, and deaths?