Have you had a flu shot? As an adult? Obviously I have no idea what happened with you when you were a child, but billions of people routinely get vaccines without excruciating or unbearable pain.
I never had a flu shot as an adult, but I do remember being hospitalized with Lyme disease when I was a child, and the pain of the I.V. line going into my arm was more excruciating than the pain of a vaccination and the pain of a beesting combined. Between the pain of the I.V. line and the pain of vaccinations, I harboured intense, passionate hatred towards the medical community as a child; the E.R. doctors were extremely evil people who deserved to go to jail as far as I was concerned. The E.R. doctors were as evil as the wasps and the bees who stung me.