🔬 What is a Vaccine?
A vaccine is a biological substance that stimulates the immune system to produce immunity against a specific disease. It prevents illness by preparing the body to fight infection without causing the disease itself.
🧬 How Vaccines Work
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A vaccine contains weakened, killed, or parts of a virus or bacteria (like proteins or mRNA).
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When introduced into the body, it trains the immune system to recognize and respond to the pathogen.
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If the real virus or bacteria enters the body later, the immune system responds quickly to destroy it.
📜 History & Origin
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Origin of term: From Latin "vacca" (cow)
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Invented by: Edward Jenner (1796), English doctor
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First vaccine: For smallpox, using cowpox virus
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Jenner discovered that milkmaids who had cowpox didn’t catch smallpox — he used this idea to develop immunity in others.
💉 Modern Vaccines
Modern vaccines protect against many deadly diseases:
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Viral: measles, polio, influenza, hepatitis, COVID-19
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Bacterial: tetanus, diphtheria, pertussis (whooping cough), tuberculosis
Types of modern vaccines:
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Inactivated vaccines (e.g., polio)
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Live attenuated vaccines (e.g., measles)
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mRNA vaccines (e.g., Pfizer-BioNTech COVID-19)
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Vector-based vaccines (e.g., Sputnik V, AstraZeneca)
🌍 Importance
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Prevents millions of deaths annually
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Eradicated smallpox, nearly eliminated polio
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Essential in pandemics (e.g., COVID-19)
✅ Summary
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Stimulates immune system without causing disease
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First developed in 1796 for smallpox
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Now used worldwide for dozens of diseases
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Saves lives, protects communities, supports global health