“Haven’t they determined that the efficacy of the Flu Shot is ~10%?”
You can still get the flu after the vaccine. Your system gets overwhelmed. But the antibodies will lessen the severity. If you don’t have much exposure, you probably will not get the flu. I’ve had the flu once in 10 years and I get the vaccine every year. My doctor gets it every 3 years and he gets the vaccine. If you get the flu, get Tamiflu for everyone in the household.
It's true. Your dog can still get rabies after years of vaccines too. No vaccine is perfect. They don't really know all the "whyfors" of those things yet.
Medicine is an art, not a science. Sometimes sh*t just happens. And don't worry too much because the handle on the grocery cart is probably the best vaccine of your life for the common bad guys.