well they can plainly see that the flu shot (and covid ones for that matter) just don't work that well, with plenty of patients they know got those shots showing back up at the clinic anyways with those diseases. and the flu/covid just aren't that dangerous unless you have some other complicating condition anyways, so why risk the side effects for marginal protection against something that is not that severe?   note that this is different from some other vaccines, like measles, whooping cough, or polio. vaccines actually work most of the time in protecting you from those diseases, and they are much nastier than the flu or a bad cold. so risking the side effects is probably worth it. probably i say, as while those vaccines themselves are probably fine, people are no longer trusting the other stuff used as preservatives and the like for the vaccines.
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