Years ago, I listened to an NPR interview with the lady at the CDC in charge of figuring out the flu shot each year. She inadvertently convinced me to stop getting shots. The interviewer asked her if she had gotten hers yet and she said "No, I don't get them, I'm healthy and young and they really are not that effective."
I was astonished, but she ran through the numbers, which were like "You only get exposed to flu about once a decade, the flu shot is only effective against about 2/3rds of the flu types that will be extant that year, and it's only about 80% effective against those.)
She then explained how it was a public health issue, not an individual issue, which I selfishly misunderstood.
I get them now.