[gus_massa]

Is this really a problem? To extract blood the nurse must aim for a vein, and it's a long process with many steps, and sometimes they must retry a few times before success.

And I think for the vaccine they use a part of the arm without major veins, to avoid complications, bleeding and bruises.

[tjr]

It's a potential problem. The odds are slim that they would hit a vein in the arm, but if they did, that would not be good.

I for one am confused as to why they wouldn't aspirate as standard procedure. I had to take some training on intramuscular injections a while back to help a family member, and checking for blood before proceeding with the injection was one of the major points.