This is exactly my first thought. He fainted and hit his head on the floor. A lot of people die from getting knocked out by a punch and then falling backward and hitting their head on the floor, and so a vaccine induced blood clot may have cause him to faint and hit his head on the floor.
Similarly, if these shots are leading to people's demise, it is likely that the cause of death isn't directly the shot but some second-order effect.
It sounds like Bob Sagat died of pneumonia.