It is common for most vaccines, that a person will become ill for a short time after receiving that vaccination.
But when a person receives a flu shot, we know they become sick with a mild case of the flu. At least that is how I understand this.
In the case of the Mrna shots, you are not being injected with a milder or dead version of the Covid virus.
So in this case, what exactly is it that people become sick with for a few days after receiving the "jab"?
It's covid, exactly the same except focused and localized. Clots and immune reaction (inflammation). Because it's the arm, the clots and the spike infection that produces them mostly go straight to the heart. If the person is healthy the infection will go away, but the clots cause damage anyway.