Antivaccination movements historically pop up in all kinds of different places and contexts for different nominal reasons, and I'm pretty sure a big part of what gives them steam is that people just aren't comfortable with the physical logistics.
Since it's on the side it doesn't affect me that much, but I feel it for much longer than I feel the needle that's been in my arm for 10+ minutes.
I had various nurses as a child and the pressure/closeness the puncture tool was applied with, matters more than anything. With any puncture tool, if its already being pushed into flesh, ie. skin is forming a valley, its more likely to cut through deeper layers due to the compression.
then again I am a big chicken when it comes to shots
When I was 11 I was in the hospital. A nurse was going to replace my IV. She spent 45 minutes trying to find a vein in either arm. She got another nurse and within 5 minutes, it was done.
The new nurse said that the previous one just got done trying to put an IV in an infant so she was "a little stressed" and "should have known better" about not stabbing a child for 45 minutes straight.
That experience was pure hell. It hurt so much. I was so sick that I could barely move or talk to ask for someone new. All I could do was lay there screaming in my mind and sort of move every once in a while.