Innate defenses react within minutes; adaptive immunity takes days but builds memory — the basis of vaccines.
How it works, step by step
Barriers (skin, mucus, stomach acid) block most invaders.
Innate cells recognize general danger signals and attack.
Lymphocytes learn the specific invader and multiply.
Memory cells remain for faster responses next time.
Nutrition
Deficiencies of protein, zinc, vitamin A, C or D impair immunity. Extra beyond adequacy hasn't been shown to 'supercharge' it in healthy people.
Evidence & sources
Vaccines work by training the immune system to recognize a germ and build memory without causing the disease. Evidence: established. Known: Foundational immunology. Unknown: — Source: World Health Organization, How do vaccines work? (Current revision).