When you get a shot for a vaccine (for example, the annual flu vaccine), the nurse frequently indicates that your arm will ache for a day or two, maybe more. This ache is typically not just a pain from having your skin punctured, but is actually an ache of the entire arm.
What mechanism causes the entire arm to ache from a vaccine? Why doesn't that ache extend to other parts of the body, like the hands or the shoulders? Why do non-vaccine arm punctures (such as drawing blood, injecting drugs) not cause the ache?