If you still got the flu it doesn't necessarily mean you got a different strain. Vaccination AND infection prime your body to create long lived producers of virus specific antibodies to provide many built in processes of your immune system with immensely better targeting. This process can take days during which your bodies immune system will function but not at an optimum level.
Vaccination isn't a guarantee that you wont get sick. Picture your body like Omaha beach on D-Day the more boats landing the better the chances that the invasion makes it past the beach no matter how well armed the defenders.
If you are 18-50 the risk of the flu isn't very high but the risk of the shot is comparatively microscopic. It's still worth it on net and it decreases the chances of infecting someone less healthy or older who as mentioned before is imperfectly protected by vaccination alone. You not spreading or as much is fewer invaders on their beach.
Vaccination isn't a guarantee that you wont get sick. Picture your body like Omaha beach on D-Day the more boats landing the better the chances that the invasion makes it past the beach no matter how well armed the defenders.
If you are 18-50 the risk of the flu isn't very high but the risk of the shot is comparatively microscopic. It's still worth it on net and it decreases the chances of infecting someone less healthy or older who as mentioned before is imperfectly protected by vaccination alone. You not spreading or as much is fewer invaders on their beach.
Anyway I highly recommend "In Defense of Self" https://www.amazon.com/Defense-Self-Immune-System-Really/dp/... its a little old but well written and comprehensible.