What is vaccine? How does it develop immunity in a person?

Explanation

### Step-by-Step Solution

**Step 1: Definition of Vaccine**
A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. It typically contains killed or weakened forms of the pathogen (germs), or parts of the pathogen (like proteins or sugars), that cause the disease.

**Step 2: Components of Vaccines**
Vaccines can contain:
- Killed germs (inactivated pathogens)
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