Your immune system builds a tolerance once your body battles off the flu!! I had the Hong Kong flu OMG thought I would die from that damn thing was flat on my back for 2 weeks BUT it ran its course and I have never had a flu shot and never had the flu after that!! That flu was NASTY I have had severe colds a bout with bronchitis once but never had the flu again!!!
LOL...having a really bad case of the flu ( I had the Asian Flu and damned near died from it; as a kid )appears to give some immunity for the rest of their lives. I’ve NEVER had any flu again either and can’t have a flu shot.
Apparently with this, people have gotten re-infected. People are not holding on to the immunity.
Great. Glad that worked out for you that way.