Name two diseases which can be prevented by using vaccines.

Explanation

### Step-by-Step Solution:

1. **Understanding Vaccines**: Vaccines are biological preparations that provide immunity to a particular disease. They contain weakened or killed forms of pathogens (bacteria or viruses) that stimulate the immune system to recognize and fight these pathogens in the future.

2. **Role of Vaccines**: When a vaccine is administered, it helps the body to develop immunity against specific diseases. This process is known as immunization. The immune system learns to recognize the pathogen and can respond more effectively if it encounters the same pathogen later.

3. **Identifying Diseases Prevented by Vaccines**: There are several diseases that can be prevented through vaccination. Two well-known examples are:
- **Smallpox**: A highly contagious and deadly disease that has been eradicated due to successful vaccination programs.
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