I had the stomach flu once as a teen. Worst experience ever, uncontrollable puking, dry heaving, I couldn't even keep water down for more than 5 minutes, and I only drank anything to keep the dry heaving from hurting more. Imagine that hell for hours on end.       I've never had the flu as an adult. I've never had a flu shot. in fact, I very rarely get sick with anything and it's usually mild and many years apart.     I probably have a decent immune system, but I know I'm not invincible. Part of why I don't get sick is because I follow protocols, like not touching public doors with my bare hands, using hand sanitizer after shaking someones hand, not touching my face after, stuff like that.