ELI5: vaccines

high confidence

March 26, 2026health

// explanation

// eli5

What is a vaccine?

A vaccine is like a practice drill for your body's defense team [5]. It shows your immune system what a bad germ looks like without actually making you sick, so your body learns how to fight it [1][3].

Why does your body need vaccines?

Your body has soldiers called white blood cells that protect you from germs [5]. Vaccines train these soldiers by showing them pictures of dangerous germs before the real germs attack, so they're ready to fight [3].

What happens when you get a vaccine?

When you get a vaccine, your body's defense team practices fighting the germ and remembers what it looks like [5]. If the real germ ever tries to invade, your body recognizes it immediately and defeats it before you get sick [1][3].

How do vaccines keep you healthy?

Vaccines protect you from serious diseases like measles, polio, and COVID-19 [3]. They also help protect people around you who can't get vaccinated, like babies and people with allergies [1].

// sources

[1]Vaccines & Immunizations - CDC

Vaccine Schedules For You and Your Family. Stay up to date on getting recommended vaccines for you and your family.

[2]Vaccines | An Open Access Journal from MDPI

Vaccines. Vaccines is an international, peer-reviewed, open access journal on laboratory and clinical vaccine research, utilization and immunization, published ...

[3]Vaccines and immunization - World Health Organization (WHO)

Vaccines protect against many different diseases, including: cervical cancer; cholera; COVID-19; dengue; diphtheria; Ebola; hepatitis B; influenza; Japanese ...

[4]Vaccines - FDA

Jan 15, 2025 ... Vaccines, as with all products regulated by FDA, undergo a rigorous review of laboratory and clinical data to ensure the safety, efficacy, purity and potency ...

[5]Vaccine - Wikipedia

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease.

[6]mRNA vaccines, explainedvideo

Video by Vox