Vaccination for small pox lasts for life time whereas vaccination for typhoid lasts for 2-3 years. Give reason.

Explanation

**Step-by-Step Solution:**

1. **Understanding Vaccination**: Vaccination involves introducing a harmless form of a pathogen (either dead or weakened) into the body. This stimulates the immune system to respond without causing the disease.

2. **Immune Response**: When the vaccine is administered, the immune system recognizes the pathogen and produces antibodies. It also creates memory cells that remember the pathogen.

3. **Long-term Immunity**: In the case of smallpox vaccination, the memory cells generated are capable of producing antibodies for a lifetime. This means that even if the individual is exposed to the smallpox virus later in life, their immune system can respond quickly and effectively, preventing the disease.

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