I have never had flu, not even in 1957, when there was an often forgotten flu epidemic, that led to schools and factories closing. I was at boarding school sleeping in an open dormitory with 15 other girls. Neither I, nor my sisters caught flu. None of my family had it. My father was in the army working on a large army base, he stayed flu free.
For the first few years after I became eligible for it I did not have the flu jab but then someone (medical) pointed out to me, that, while the flu jab specifically protected me from flu, which was probably unnecessary in my case, it also boosted my immune system generally making it possible for me to better fight off any other infections that came my way.
I now have the flu jab.