I've been getting the annual flu shot for years. I did get the flu once several years back, wasn't bad.  I seldom get sick.  I see the doctor once a year, get about 5 blood tests and get a prescription renewal for a blood pressure med.

I would think by this time I should be resistant to all the different flu's.

When my wife returned from a trip with Covid I slept next to her, ate at the table with her and changed nothing in our day today routine. I had a couple of the Covid shots months before and then said no to anymore.  She on the other hand had all that were available to that point.