You're right, every disease we catch gives us complete immunity. That's why when you catch the flu once, you're immune to it forever. I'm being sardonic here b

You're right, every disease we catch gives us complete immunity. That's why when you catch the flu once, you're immune to it forever. I'm being sardonic here because you have a severe misunderstanding of how immunity and our immune system actually works. Some diseases (like the chicken pox) we never truly beat, it just becomes latent. Other diseases we only become briefly immune.