Principle of vaccination is based on the property of "memory" of the immune system. Taking one suitable example, justify the statement.

Explanation

To justify the statement that the principle of vaccination is based on the property of "memory" of the immune system, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Immune Response**:
- When a pathogen (like a virus or bacteria) enters the body, the immune system responds by activating various immune cells, primarily T lymphocytes and B lymphocytes. These cells work together to identify and eliminate the pathogen.

**Hint**: The immune system's response is crucial for protecting the body from infections.
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